patch, 19 partsAdd new command "switch"

diff --git a/Documentation/git-checkout.txt b/Documentation/git-checkout.txt
index ce7d38b8b7..bc7fbdb8d2 100644
--- a/Documentation/git-checkout.txt
+++ b/Documentation/git-checkout.txt
@@ -23,7 +23,7 @@ or the specified tree.  If no paths are given, 'git checkout' will
 also update `HEAD` to set the specified branch as the current
 branch.
 
-'git checkout' <branch>::
+'git checkout' [<branch>]::
 	To prepare for working on <branch>, switch to it by updating
 	the index and the files in the working tree, and by pointing
 	HEAD at the branch. Local modifications to the files in the

Documentation/git-checkout.txt, Documentation/git-merge.txt

diff --git a/Documentation/git-checkout.txt b/Documentation/git-checkout.txt
index bc7fbdb8d2..9ac01f7967 100644
--- a/Documentation/git-checkout.txt
+++ b/Documentation/git-checkout.txt
@@ -270,6 +270,11 @@ Note that this option uses the no overlay mode by default (see also
 	out anyway. In other words, the ref can be held by more than one
 	worktree.
 
+--[no-]overwrite-ignore::
+	Silently overwrite ignored files when switching branches. This
+	is the default behavior. Use --no-overwrite-ignore to abort
+	the operation when the new branch contains ignored files.
+
 --[no-]recurse-submodules::
 	Using --recurse-submodules will update the content of all initialized
 	submodules according to the commit recorded in the superproject. If
diff --git a/Documentation/git-merge.txt b/Documentation/git-merge.txt
index 4cc86469f3..0480e9d0f0 100644
--- a/Documentation/git-merge.txt
+++ b/Documentation/git-merge.txt
@@ -87,6 +87,10 @@ will be appended to the specified message.
 	Allow the rerere mechanism to update the index with the
 	result of auto-conflict resolution if possible.
 
+--[no-]overwrite-ignore::
+	Silently overwrite ignored files from the merge result. This
+	is the default behavior. Use --no-overwrite-ignore to abort.
+
 --abort::
 	Abort the current conflict resolution process, and
 	try to reconstruct the pre-merge state.

diff --git a/t/t2014-switch.sh b/t/t2014-checkout-switch.sh
similarity index 100%
rename from t/t2014-switch.sh
rename to t/t2014-checkout-switch.sh

diff --git a/builtin/checkout.c b/builtin/checkout.c
index f63d864a91..12b7e08d4e 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -1068,6 +1068,34 @@ static int git_checkout_config(const char *var, const char *value, void *cb)
 	return git_xmerge_config(var, value, NULL);
 }
 
+static void setup_new_branch_info_and_source_tree(
+	struct branch_info *new_branch_info,
+	struct checkout_opts *opts,
+	struct object_id *rev,
+	const char *arg)
+{
+	struct tree **source_tree = &opts->source_tree;
+	struct object_id branch_rev;
+
+	new_branch_info->name = arg;
+	setup_branch_path(new_branch_info);
+
+	if (!check_refname_format(new_branch_info->path, 0) &&
+	    !read_ref(new_branch_info->path, &branch_rev))
+		oidcpy(rev, &branch_rev);
+	else
+		new_branch_info->path = NULL; /* not an existing branch */
+
+	new_branch_info->commit = lookup_commit_reference_gently(the_repository, rev, 1);
+	if (!new_branch_info->commit) {
+		/* not a commit */
+		*source_tree = parse_tree_indirect(rev);
+	} else {
+		parse_commit_or_die(new_branch_info->commit);
+		*source_tree = get_commit_tree(new_branch_info->commit);
+	}
+}
+
 static int parse_branchname_arg(int argc, const char **argv,
 				int dwim_new_local_branch_ok,
 				struct branch_info *new_branch_info,
@@ -1075,10 +1103,8 @@ static int parse_branchname_arg(int argc, const char **argv,
 				struct object_id *rev,
 				int *dwim_remotes_matched)
 {
-	struct tree **source_tree = &opts->source_tree;
 	const char **new_branch = &opts->new_branch;
 	int argcount = 0;
-	struct object_id branch_rev;
 	const char *arg;
 	int dash_dash_pos;
 	int has_dash_dash = 0;
@@ -1200,26 +1226,11 @@ static int parse_branchname_arg(int argc, const char **argv,
 	argv++;
 	argc--;
 
-	new_branch_info->name = arg;
-	setup_branch_path(new_branch_info);
-
-	if (!check_refname_format(new_branch_info->path, 0) &&
-	    !read_ref(new_branch_info->path, &branch_rev))
-		oidcpy(rev, &branch_rev);
-	else
-		new_branch_info->path = NULL; /* not an existing branch */
+	setup_new_branch_info_and_source_tree(new_branch_info, opts, rev, arg);
 
-	new_branch_info->commit = lookup_commit_reference_gently(the_repository, rev, 1);
-	if (!new_branch_info->commit) {
-		/* not a commit */
-		*source_tree = parse_tree_indirect(rev);
-	} else {
-		parse_commit_or_die(new_branch_info->commit);
-		*source_tree = get_commit_tree(new_branch_info->commit);
-	}
-
-	if (!*source_tree)                   /* case (1): want a tree */
+	if (!opts->source_tree)                   /* case (1): want a tree */
 		die(_("reference is not a tree: %s"), arg);
+
 	if (!has_dash_dash) {	/* case (3).(d) -> (1) */
 		/*
 		 * Do not complain the most common case

diff --git a/builtin/checkout.c b/builtin/checkout.c
index 12b7e08d4e..66f99e788d 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -1326,82 +1326,83 @@ static int checkout_branch(struct checkout_opts *opts,
 
 int cmd_checkout(int argc, const char **argv, const char *prefix)
 {
-	struct checkout_opts opts;
+	struct checkout_opts real_opts;
+	struct checkout_opts *opts = &real_opts;
 	struct branch_info new_branch_info;
 	char *conflict_style = NULL;
 	int dwim_new_local_branch, no_dwim_new_local_branch = 0;
 	int dwim_remotes_matched = 0;
 	struct option options[] = {
-		OPT__QUIET(&opts.quiet, N_("suppress progress reporting")),
-		OPT_STRING('b', NULL, &opts.new_branch, N_("branch"),
+		OPT__QUIET(&opts->quiet, N_("suppress progress reporting")),
+		OPT_STRING('b', NULL, &opts->new_branch, N_("branch"),
 			   N_("create and checkout a new branch")),
-		OPT_STRING('B', NULL, &opts.new_branch_force, N_("branch"),
+		OPT_STRING('B', NULL, &opts->new_branch_force, N_("branch"),
 			   N_("create/reset and checkout a branch")),
-		OPT_BOOL('l', NULL, &opts.new_branch_log, N_("create reflog for new branch")),
-		OPT_BOOL(0, "detach", &opts.force_detach, N_("detach HEAD at named commit")),
-		OPT_SET_INT('t', "track",  &opts.track, N_("set upstream info for new branch"),
+		OPT_BOOL('l', NULL, &opts->new_branch_log, N_("create reflog for new branch")),
+		OPT_BOOL(0, "detach", &opts->force_detach, N_("detach HEAD at named commit")),
+		OPT_SET_INT('t', "track",  &opts->track, N_("set upstream info for new branch"),
 			BRANCH_TRACK_EXPLICIT),
-		OPT_STRING(0, "orphan", &opts.new_orphan_branch, N_("new-branch"), N_("new unparented branch")),
-		OPT_SET_INT_F('2', "ours", &opts.writeout_stage,
+		OPT_STRING(0, "orphan", &opts->new_orphan_branch, N_("new-branch"), N_("new unparented branch")),
+		OPT_SET_INT_F('2', "ours", &opts->writeout_stage,
 			      N_("checkout our version for unmerged files"),
 			      2, PARSE_OPT_NONEG),
-		OPT_SET_INT_F('3', "theirs", &opts.writeout_stage,
+		OPT_SET_INT_F('3', "theirs", &opts->writeout_stage,
 			      N_("checkout their version for unmerged files"),
 			      3, PARSE_OPT_NONEG),
-		OPT__FORCE(&opts.force, N_("force checkout (throw away local modifications)"),
+		OPT__FORCE(&opts->force, N_("force checkout (throw away local modifications)"),
 			   PARSE_OPT_NOCOMPLETE),
-		OPT_BOOL('m', "merge", &opts.merge, N_("perform a 3-way merge with the new branch")),
-		OPT_BOOL_F(0, "overwrite-ignore", &opts.overwrite_ignore,
+		OPT_BOOL('m', "merge", &opts->merge, N_("perform a 3-way merge with the new branch")),
+		OPT_BOOL_F(0, "overwrite-ignore", &opts->overwrite_ignore,
 			   N_("update ignored files (default)"),
 			   PARSE_OPT_NOCOMPLETE),
 		OPT_STRING(0, "conflict", &conflict_style, N_("style"),
 			   N_("conflict style (merge or diff3)")),
-		OPT_BOOL('p', "patch", &opts.patch_mode, N_("select hunks interactively")),
-		OPT_BOOL(0, "ignore-skip-worktree-bits", &opts.ignore_skipworktree,
+		OPT_BOOL('p', "patch", &opts->patch_mode, N_("select hunks interactively")),
+		OPT_BOOL(0, "ignore-skip-worktree-bits", &opts->ignore_skipworktree,
 			 N_("do not limit pathspecs to sparse entries only")),
 		OPT_BOOL(0, "no-guess", &no_dwim_new_local_branch,
 			 N_("do not second guess 'git checkout <no-such-branch>'")),
-		OPT_BOOL(0, "ignore-other-worktrees", &opts.ignore_other_worktrees,
+		OPT_BOOL(0, "ignore-other-worktrees", &opts->ignore_other_worktrees,
 			 N_("do not check if another worktree is holding the given ref")),
 		{ OPTION_CALLBACK, 0, "recurse-submodules", NULL,
 			    "checkout", "control recursive updating of submodules",
 			    PARSE_OPT_OPTARG, option_parse_recurse_submodules_worktree_updater },
-		OPT_BOOL(0, "progress", &opts.show_progress, N_("force progress reporting")),
-		OPT_BOOL(0, "overlay", &opts.overlay_mode, N_("use overlay mode (default)")),
+		OPT_BOOL(0, "progress", &opts->show_progress, N_("force progress reporting")),
+		OPT_BOOL(0, "overlay", &opts->overlay_mode, N_("use overlay mode (default)")),
 		OPT_END(),
 	};
 
-	memset(&opts, 0, sizeof(opts));
+	memset(opts, 0, sizeof(*opts));
 	memset(&new_branch_info, 0, sizeof(new_branch_info));
-	opts.overwrite_ignore = 1;
-	opts.prefix = prefix;
-	opts.show_progress = -1;
-	opts.overlay_mode = -1;
+	opts->overwrite_ignore = 1;
+	opts->prefix = prefix;
+	opts->show_progress = -1;
+	opts->overlay_mode = -1;
 
-	git_config(git_checkout_config, &opts);
+	git_config(git_checkout_config, opts);
 
-	opts.track = BRANCH_TRACK_UNSPECIFIED;
+	opts->track = BRANCH_TRACK_UNSPECIFIED;
 
 	argc = parse_options(argc, argv, prefix, options, checkout_usage,
 			     PARSE_OPT_KEEP_DASHDASH);
 
 	dwim_new_local_branch = !no_dwim_new_local_branch;
-	if (opts.show_progress < 0) {
-		if (opts.quiet)
-			opts.show_progress = 0;
+	if (opts->show_progress < 0) {
+		if (opts->quiet)
+			opts->show_progress = 0;
 		else
-			opts.show_progress = isatty(2);
+			opts->show_progress = isatty(2);
 	}
 
 	if (conflict_style) {
-		opts.merge = 1; /* implied */
+		opts->merge = 1; /* implied */
 		git_xmerge_config("merge.conflictstyle", conflict_style, NULL);
 	}
 
-	if ((!!opts.new_branch + !!opts.new_branch_force + !!opts.new_orphan_branch) > 1)
+	if ((!!opts->new_branch + !!opts->new_branch_force + !!opts->new_orphan_branch) > 1)
 		die(_("-b, -B and --orphan are mutually exclusive"));
 
-	if (opts.overlay_mode == 1 && opts.patch_mode)
+	if (opts->overlay_mode == 1 && opts->patch_mode)
 		die(_("-p and --overlay are mutually exclusive"));
 
 	/*
@@ -1409,14 +1410,14 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 	 * and new_branch_force and new_orphan_branch will tell us which one of
 	 * -b/-B/--orphan is being used.
 	 */
-	if (opts.new_branch_force)
-		opts.new_branch = opts.new_branch_force;
+	if (opts->new_branch_force)
+		opts->new_branch = opts->new_branch_force;
 
-	if (opts.new_orphan_branch)
-		opts.new_branch = opts.new_orphan_branch;
+	if (opts->new_orphan_branch)
+		opts->new_branch = opts->new_orphan_branch;
 
 	/* --track without -b/-B/--orphan should DWIM */
-	if (opts.track != BRANCH_TRACK_UNSPECIFIED && !opts.new_branch) {
+	if (opts->track != BRANCH_TRACK_UNSPECIFIED && !opts->new_branch) {
 		const char *argv0 = argv[0];
 		if (!argc || !strcmp(argv0, "--"))
 			die(_("--track needs a branch name"));
@@ -1425,7 +1426,7 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 		argv0 = strchr(argv0, '/');
 		if (!argv0 || !argv0[1])
 			die(_("missing branch name; try -b"));
-		opts.new_branch = argv0 + 1;
+		opts->new_branch = argv0 + 1;
 	}
 
 	/*
@@ -1444,56 +1445,56 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 	if (argc) {
 		struct object_id rev;
 		int dwim_ok =
-			!opts.patch_mode &&
+			!opts->patch_mode &&
 			dwim_new_local_branch &&
-			opts.track == BRANCH_TRACK_UNSPECIFIED &&
-			!opts.new_branch;
+			opts->track == BRANCH_TRACK_UNSPECIFIED &&
+			!opts->new_branch;
 		int n = parse_branchname_arg(argc, argv, dwim_ok,
-					     &new_branch_info, &opts, &rev,
+					     &new_branch_info, opts, &rev,
 					     &dwim_remotes_matched);
 		argv += n;
 		argc -= n;
 	}
 
 	if (argc) {
-		parse_pathspec(&opts.pathspec, 0,
-			       opts.patch_mode ? PATHSPEC_PREFIX_ORIGIN : 0,
+		parse_pathspec(&opts->pathspec, 0,
+			       opts->patch_mode ? PATHSPEC_PREFIX_ORIGIN : 0,
 			       prefix, argv);
 
-		if (!opts.pathspec.nr)
+		if (!opts->pathspec.nr)
 			die(_("invalid path specification"));
 
 		/*
 		 * Try to give more helpful suggestion.
 		 * new_branch && argc > 1 will be caught later.
 		 */
-		if (opts.new_branch && argc == 1)
+		if (opts->new_branch && argc == 1)
 			die(_("'%s' is not a commit and a branch '%s' cannot be created from it"),
-				argv[0], opts.new_branch);
+				argv[0], opts->new_branch);
 
-		if (opts.force_detach)
+		if (opts->force_detach)
 			die(_("git checkout: --detach does not take a path argument '%s'"),
 			    argv[0]);
 
-		if (1 < !!opts.writeout_stage + !!opts.force + !!opts.merge)
+		if (1 < !!opts->writeout_stage + !!opts->force + !!opts->merge)
 			die(_("git checkout: --ours/--theirs, --force and --merge are incompatible when\n"
 			      "checking out of the index."));
 	}
 
-	if (opts.new_branch) {
+	if (opts->new_branch) {
 		struct strbuf buf = STRBUF_INIT;
 
-		if (opts.new_branch_force)
-			opts.branch_exists = validate_branchname(opts.new_branch, &buf);
+		if (opts->new_branch_force)
+			opts->branch_exists = validate_branchname(opts->new_branch, &buf);
 		else
-			opts.branch_exists =
-				validate_new_branchname(opts.new_branch, &buf, 0);
+			opts->branch_exists =
+				validate_new_branchname(opts->new_branch, &buf, 0);
 		strbuf_release(&buf);
 	}
 
 	UNLEAK(opts);
-	if (opts.patch_mode || opts.pathspec.nr) {
-		int ret = checkout_paths(&opts, new_branch_info.name);
+	if (opts->patch_mode || opts->pathspec.nr) {
+		int ret = checkout_paths(opts, new_branch_info.name);
 		if (ret && dwim_remotes_matched > 1 &&
 		    advice_checkout_ambiguous_remote_branch_name)
 			advise(_("'%s' matched more than one remote tracking branch.\n"
@@ -1512,6 +1513,6 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 			       dwim_remotes_matched);
 		return ret;
 	} else {
-		return checkout_branch(&opts, &new_branch_info);
+		return checkout_branch(opts, &new_branch_info);
 	}
 }

diff --git a/builtin/checkout.c b/builtin/checkout.c
index 66f99e788d..5914dd3619 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -46,6 +46,8 @@ struct checkout_opts {
 	int show_progress;
 	int count_checkout_paths;
 	int overlay_mode;
+	int no_dwim_new_local_branch;
+
 	/*
 	 * If new checkout options are added, skip_merge_working_tree
 	 * should be updated accordingly.
@@ -57,6 +59,7 @@ struct checkout_opts {
 	int new_branch_log;
 	enum branch_track track;
 	struct diff_options diff_options;
+	char *conflict_style;
 
 	int branch_exists;
 	const char *prefix;
@@ -1329,8 +1332,7 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 	struct checkout_opts real_opts;
 	struct checkout_opts *opts = &real_opts;
 	struct branch_info new_branch_info;
-	char *conflict_style = NULL;
-	int dwim_new_local_branch, no_dwim_new_local_branch = 0;
+	int dwim_new_local_branch;
 	int dwim_remotes_matched = 0;
 	struct option options[] = {
 		OPT__QUIET(&opts->quiet, N_("suppress progress reporting")),
@@ -1355,12 +1357,12 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 		OPT_BOOL_F(0, "overwrite-ignore", &opts->overwrite_ignore,
 			   N_("update ignored files (default)"),
 			   PARSE_OPT_NOCOMPLETE),
-		OPT_STRING(0, "conflict", &conflict_style, N_("style"),
+		OPT_STRING(0, "conflict", &opts->conflict_style, N_("style"),
 			   N_("conflict style (merge or diff3)")),
 		OPT_BOOL('p', "patch", &opts->patch_mode, N_("select hunks interactively")),
 		OPT_BOOL(0, "ignore-skip-worktree-bits", &opts->ignore_skipworktree,
 			 N_("do not limit pathspecs to sparse entries only")),
-		OPT_BOOL(0, "no-guess", &no_dwim_new_local_branch,
+		OPT_BOOL(0, "no-guess", &opts->no_dwim_new_local_branch,
 			 N_("do not second guess 'git checkout <no-such-branch>'")),
 		OPT_BOOL(0, "ignore-other-worktrees", &opts->ignore_other_worktrees,
 			 N_("do not check if another worktree is holding the given ref")),
@@ -1378,6 +1380,7 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 	opts->prefix = prefix;
 	opts->show_progress = -1;
 	opts->overlay_mode = -1;
+	opts->no_dwim_new_local_branch = 0;
 
 	git_config(git_checkout_config, opts);
 
@@ -1386,7 +1389,7 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 	argc = parse_options(argc, argv, prefix, options, checkout_usage,
 			     PARSE_OPT_KEEP_DASHDASH);
 
-	dwim_new_local_branch = !no_dwim_new_local_branch;
+	dwim_new_local_branch = !opts->no_dwim_new_local_branch;
 	if (opts->show_progress < 0) {
 		if (opts->quiet)
 			opts->show_progress = 0;
@@ -1394,9 +1397,9 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 			opts->show_progress = isatty(2);
 	}
 
-	if (conflict_style) {
+	if (opts->conflict_style) {
 		opts->merge = 1; /* implied */
-		git_xmerge_config("merge.conflictstyle", conflict_style, NULL);
+		git_xmerge_config("merge.conflictstyle", opts->conflict_style, NULL);
 	}
 
 	if ((!!opts->new_branch + !!opts->new_branch_force + !!opts->new_orphan_branch) > 1)

builtin/checkout.c, parse-options-cb.c, parse-options.h

diff --git a/builtin/checkout.c b/builtin/checkout.c
index 5914dd3619..8ea1349cce 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -1327,15 +1327,31 @@ static int checkout_branch(struct checkout_opts *opts,
 	return switch_branches(opts, new_branch_info);
 }
 
-int cmd_checkout(int argc, const char **argv, const char *prefix)
+static struct option *add_common_options(struct checkout_opts *opts,
+					 struct option *prevopts)
 {
-	struct checkout_opts real_opts;
-	struct checkout_opts *opts = &real_opts;
-	struct branch_info new_branch_info;
-	int dwim_new_local_branch;
-	int dwim_remotes_matched = 0;
 	struct option options[] = {
 		OPT__QUIET(&opts->quiet, N_("suppress progress reporting")),
+		{ OPTION_CALLBACK, 0, "recurse-submodules", NULL,
+			    "checkout", "control recursive updating of submodules",
+			    PARSE_OPT_OPTARG, option_parse_recurse_submodules_worktree_updater },
+		OPT_BOOL(0, "progress", &opts->show_progress, N_("force progress reporting")),
+		OPT__FORCE(&opts->force, N_("force checkout (throw away local modifications)"),
+			   PARSE_OPT_NOCOMPLETE),
+		OPT_BOOL('m', "merge", &opts->merge, N_("perform a 3-way merge with the new branch")),
+		OPT_STRING(0, "conflict", &opts->conflict_style, N_("style"),
+			   N_("conflict style (merge or diff3)")),
+		OPT_END()
+	};
+	struct option *newopts = parse_options_concat(prevopts, options);
+	free(prevopts);
+	return newopts;
+}
+
+static struct option *add_switch_branch_options(struct checkout_opts *opts,
+						struct option *prevopts)
+{
+	struct option options[] = {
 		OPT_STRING('b', NULL, &opts->new_branch, N_("branch"),
 			   N_("create and checkout a new branch")),
 		OPT_STRING('B', NULL, &opts->new_branch_force, N_("branch"),
@@ -1345,34 +1361,49 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 		OPT_SET_INT('t', "track",  &opts->track, N_("set upstream info for new branch"),
 			BRANCH_TRACK_EXPLICIT),
 		OPT_STRING(0, "orphan", &opts->new_orphan_branch, N_("new-branch"), N_("new unparented branch")),
+		OPT_BOOL_F(0, "overwrite-ignore", &opts->overwrite_ignore,
+			   N_("update ignored files (default)"),
+			   PARSE_OPT_NOCOMPLETE),
+		OPT_BOOL(0, "no-guess", &opts->no_dwim_new_local_branch,
+			 N_("second guess 'git checkout <no-such-branch>'")),
+		OPT_BOOL(0, "ignore-other-worktrees", &opts->ignore_other_worktrees,
+			 N_("do not check if another worktree is holding the given ref")),
+		OPT_END()
+	};
+	struct option *newopts = parse_options_concat(prevopts, options);
+	free(prevopts);
+	return newopts;
+}
+
+static struct option *add_checkout_path_options(struct checkout_opts *opts,
+						struct option *prevopts)
+{
+	struct option options[] = {
 		OPT_SET_INT_F('2', "ours", &opts->writeout_stage,
 			      N_("checkout our version for unmerged files"),
 			      2, PARSE_OPT_NONEG),
 		OPT_SET_INT_F('3', "theirs", &opts->writeout_stage,
 			      N_("checkout their version for unmerged files"),
 			      3, PARSE_OPT_NONEG),
-		OPT__FORCE(&opts->force, N_("force checkout (throw away local modifications)"),
-			   PARSE_OPT_NOCOMPLETE),
-		OPT_BOOL('m', "merge", &opts->merge, N_("perform a 3-way merge with the new branch")),
-		OPT_BOOL_F(0, "overwrite-ignore", &opts->overwrite_ignore,
-			   N_("update ignored files (default)"),
-			   PARSE_OPT_NOCOMPLETE),
-		OPT_STRING(0, "conflict", &opts->conflict_style, N_("style"),
-			   N_("conflict style (merge or diff3)")),
 		OPT_BOOL('p', "patch", &opts->patch_mode, N_("select hunks interactively")),
 		OPT_BOOL(0, "ignore-skip-worktree-bits", &opts->ignore_skipworktree,
 			 N_("do not limit pathspecs to sparse entries only")),
-		OPT_BOOL(0, "no-guess", &opts->no_dwim_new_local_branch,
-			 N_("do not second guess 'git checkout <no-such-branch>'")),
-		OPT_BOOL(0, "ignore-other-worktrees", &opts->ignore_other_worktrees,
-			 N_("do not check if another worktree is holding the given ref")),
-		{ OPTION_CALLBACK, 0, "recurse-submodules", NULL,
-			    "checkout", "control recursive updating of submodules",
-			    PARSE_OPT_OPTARG, option_parse_recurse_submodules_worktree_updater },
-		OPT_BOOL(0, "progress", &opts->show_progress, N_("force progress reporting")),
 		OPT_BOOL(0, "overlay", &opts->overlay_mode, N_("use overlay mode (default)")),
-		OPT_END(),
+		OPT_END()
 	};
+	struct option *newopts = parse_options_concat(prevopts, options);
+	free(prevopts);
+	return newopts;
+}
+
+int cmd_checkout(int argc, const char **argv, const char *prefix)
+{
+	struct checkout_opts real_opts;
+	struct checkout_opts *opts = &real_opts;
+	struct branch_info new_branch_info;
+	int dwim_remotes_matched = 0;
+	int dwim_new_local_branch;
+	struct option *options = NULL;
 
 	memset(opts, 0, sizeof(*opts));
 	memset(&new_branch_info, 0, sizeof(new_branch_info));
@@ -1386,6 +1417,11 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 
 	opts->track = BRANCH_TRACK_UNSPECIFIED;
 
+	options = parse_options_dup(options);
+	options = add_common_options(opts, options);
+	options = add_switch_branch_options(opts, options);
+	options = add_checkout_path_options(opts, options);
+
 	argc = parse_options(argc, argv, prefix, options, checkout_usage,
 			     PARSE_OPT_KEEP_DASHDASH);
 
diff --git a/parse-options-cb.c b/parse-options-cb.c
index e2f3eaed07..76eb5c211b 100644
--- a/parse-options-cb.c
+++ b/parse-options-cb.c
@@ -122,6 +122,23 @@ int parse_opt_tertiary(const struct option *opt, const char *arg, int unset)
 	return 0;
 }
 
+struct option *parse_options_dup(const struct option *o)
+{
+	struct option *opts;
+	int nr = 0;
+
+	while (o && o->type != OPTION_END) {
+		nr++;
+		o++;
+	}
+
+	ALLOC_ARRAY(opts, nr + 1);
+	memcpy(opts, o - nr, sizeof(*o) * nr);
+	memset(opts + nr, 0, sizeof(*opts));
+	opts[nr].type = OPTION_END;
+	return opts;
+}
+
 struct option *parse_options_concat(struct option *a, struct option *b)
 {
 	struct option *ret;
diff --git a/parse-options.h b/parse-options.h
index 14fe32428e..6846a5b1e0 100644
--- a/parse-options.h
+++ b/parse-options.h
@@ -237,7 +237,8 @@ extern int parse_options_step(struct parse_opt_ctx_t *ctx,
 
 extern int parse_options_end(struct parse_opt_ctx_t *ctx);
 
-extern struct option *parse_options_concat(struct option *a, struct option *b);
+struct option *parse_options_dup(const struct option *a);
+struct option *parse_options_concat(struct option *a, struct option *b);
 
 /*----- some often used options -----*/
 extern int parse_opt_abbrev_cb(const struct option *, const char *, int);

.gitignore, Documentation/config/advice.txt, Documentation/config/branch.txt, Documentation/config/checkout.txt, Documentation/config/diff.txt, Documentation/git-checkout.txt, Documentation/git-switch.txt, Documentation/gitattributes.txt, Documentation/githooks.txt, Makefile, builtin.h, builtin/checkout.c, command-list.txt, git.c

diff --git a/.gitignore b/.gitignore
index 0d77ea5894..8e2b89047f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -167,6 +167,7 @@
 /git-submodule
 /git-submodule--helper
 /git-svn
+/git-switch
 /git-symbolic-ref
 /git-tag
 /git-unpack-file
diff --git a/Documentation/config/advice.txt b/Documentation/config/advice.txt
index 88620429ea..239d479506 100644
--- a/Documentation/config/advice.txt
+++ b/Documentation/config/advice.txt
@@ -42,7 +42,8 @@ advice.*::
 		state in the output of linkgit:git-status[1], in
 		the template shown when writing commit messages in
 		linkgit:git-commit[1], and in the help message shown
-		by linkgit:git-checkout[1] when switching branch.
+		by linkgit:git-switch[1] or
+		linkgit:git-checkout[1] when switching branch.
 	statusUoption::
 		Advise to consider using the `-u` option to linkgit:git-status[1]
 		when the command takes more than 2 seconds to enumerate untracked
@@ -62,12 +63,14 @@ advice.*::
 		your information is guessed from the system username and
 		domain name.
 	detachedHead::
-		Advice shown when you used linkgit:git-checkout[1] to
-		move to the detach HEAD state, to instruct how to create
-		a local branch after the fact.
+		Advice shown when you used
+		linkgit:git-switch[1] or linkgit:git-checkout[1]
+		to move to the detach HEAD state, to instruct how to
+		create a local branch after the fact.
 	checkoutAmbiguousRemoteBranchName::
 		Advice shown when the argument to
-		linkgit:git-checkout[1] ambiguously resolves to a
+		linkgit:git-checkout[1] and linkgit:git-switch[1]
+		ambiguously resolves to a
 		remote tracking branch on more than one remote in
 		situations where an unambiguous argument would have
 		otherwise caused a remote-tracking branch to be
diff --git a/Documentation/config/branch.txt b/Documentation/config/branch.txt
index 019d60ede2..8050466159 100644
--- a/Documentation/config/branch.txt
+++ b/Documentation/config/branch.txt
@@ -1,5 +1,5 @@
 branch.autoSetupMerge::
-	Tells 'git branch' and 'git checkout' to set up new branches
+	Tells 'git branch', 'git switch' and 'git checkout' to set up new branches
 	so that linkgit:git-pull[1] will appropriately merge from the
 	starting point branch. Note that even if this option is not set,
 	this behavior can be chosen per-branch using the `--track`
@@ -11,7 +11,7 @@ branch.autoSetupMerge::
 	branch. This option defaults to true.
 
 branch.autoSetupRebase::
-	When a new branch is created with 'git branch' or 'git checkout'
+	When a new branch is created with 'git branch', 'git switch' or 'git checkout'
 	that tracks another branch, this variable tells Git to set
 	up pull to rebase instead of merge (see "branch.<name>.rebase").
 	When `never`, rebase is never automatically set to true.
diff --git a/Documentation/config/checkout.txt b/Documentation/config/checkout.txt
index 73380a8d86..fc211eca58 100644
--- a/Documentation/config/checkout.txt
+++ b/Documentation/config/checkout.txt
@@ -1,5 +1,6 @@
 checkout.defaultRemote::
-	When you run 'git checkout <something>' and only have one
+	When you run 'git checkout <something>'
+	or 'git switch <something>' and only have one
 	remote, it may implicitly fall back on checking out and
 	tracking e.g. 'origin/<something>'. This stops working as soon
 	as you have more than one remote with a '<something>'
@@ -8,8 +9,10 @@ checkout.defaultRemote::
 	disambiguation. The typical use-case is to set this to
 	`origin`.
 +
-Currently this is used by linkgit:git-checkout[1] when 'git checkout
-<something>' will checkout the '<something>' branch on another remote,
+Currently this is used by linkgit:git-switch[1] and
+linkgit:git-checkout[1] when 'git checkout <something>'
+or 'git switch <something>'
+will checkout the '<something>' branch on another remote,
 and by linkgit:git-worktree[1] when 'git worktree add' refers to a
 remote branch. This setting might be used for other checkout-like
 commands or functionality in the future.
diff --git a/Documentation/config/diff.txt b/Documentation/config/diff.txt
index e48bb987d7..b3b304ee12 100644
--- a/Documentation/config/diff.txt
+++ b/Documentation/config/diff.txt
@@ -78,7 +78,8 @@ diff.external::
 diff.ignoreSubmodules::
 	Sets the default value of --ignore-submodules. Note that this
 	affects only 'git diff' Porcelain, and not lower level 'diff'
-	commands such as 'git diff-files'. 'git checkout' also honors
+	commands such as 'git diff-files'. 'git checkout'
+	and 'git switch' also honor
 	this setting when reporting uncommitted changes. Setting it to
 	'all' disables the submodule summary normally shown by 'git commit'
 	and 'git status' when `status.submoduleSummary` is set unless it is
diff --git a/Documentation/git-checkout.txt b/Documentation/git-checkout.txt
index 9ac01f7967..31c6cbef19 100644
--- a/Documentation/git-checkout.txt
+++ b/Documentation/git-checkout.txt
@@ -556,6 +556,10 @@ $ edit frotz
 $ git add frotz
 ------------
 
+SEE ALSO
+--------
+linkgit:git-switch[1]
+
 GIT
 ---
 Part of the linkgit:git[1] suite
diff --git a/Documentation/git-switch.txt b/Documentation/git-switch.txt
new file mode 100644
index 0000000000..953c9747b2
--- /dev/null
+++ b/Documentation/git-switch.txt
@@ -0,0 +1,236 @@
+git-switch(1)
+=============
+
+NAME
+----
+git-switch - Switch branches
+
+SYNOPSIS
+--------
+[verse]
+'git switch' [<options>] [--guess] <branch>
+'git switch' [<options>] --detach [<start_point>>]
+'git switch' [<options>] [[-c|-C|--orphan] <new_branch>] [<start_point>]
+
+DESCRIPTION
+-----------
+Switch to a specified branch and update files in the working tree to
+match it. Optionally a new branch could be created with either `-c` or
+`-C`, or detach from any branch with `--detach`, along with switching.
+
+OPTIONS
+-------
+<branch>::
+	Branch to switch to.
+
+<new_branch>::
+	Name for the new branch.
+
+<start_point>::
+	The name of a commit at which to switch to before creating a
+	new branch or detach from.
++
+You can use the `"@{-N}"` syntax to refer to the N-th last
+branch/commit switched to "git switch" or "git checkout"
+operation. You may also specify `-` which is synonymous to `"@{-1}`.
++
+As a special case, you may use `"A...B"` as a shortcut for the merge
+base of `A` and `B` if there is exactly one merge base. You can leave
+out at most one of `A` and `B`, in which case it defaults to `HEAD`.
+
+-c <new_branch>::
+--create <new_branch>::
+	Create a new branch named <new_branch> and start it at
+	<start_point>; see linkgit:git-branch[1] for details.
+
+-C <new_branch>::
+--force-create <new_branch>::
+	Creates the branch <new_branch> and start it at <start_point>;
+	if it already exists, then reset it to <start_point>. This is
+	equivalent to running "git branch" with "-f"; see
+	linkgit:git-branch[1] for details.
+
+-d::
+--detach::
+	Switch to a commit for inspection and discardable
+	experiments. See the "DETACHED HEAD" section in
+	linkgit:git-checkout[1] for details.
+
+-g::
+--guess::
+	If <branch> is not found but there does exist a tracking
+	branch in exactly one remote (call it <remote>) with a
+	matching name, treat as equivalent to
++
+------------
+$ git switch -c <branch> --track <remote>/<branch>
+------------
++
+If the branch exists in multiple remotes and one of them is named by
+the `checkout.defaultRemote` configuration variable, we'll use that
+one for the purposes of disambiguation, even if the `<branch>` isn't
+unique across all remotes. Set it to e.g. `checkout.defaultRemote=origin`
+to always checkout remote branches from there if `<branch>` is
+ambiguous but exists on the 'origin' remote. See also
+`checkout.defaultRemote` in linkgit:git-config[1].
+
+-q::
+--quiet::
+	Quiet, suppress feedback messages.
+
+-f::
+--force::
+	Proceed even if the index or the working tree differs from
+	HEAD.  This is used to throw away local changes.
+
+--[no-]progress::
+	Progress status is reported on the standard error stream
+	by default when it is attached to a terminal, unless `--quiet`
+	is specified. This flag enables progress reporting even if not
+	attached to a terminal, regardless of `--quiet`.
+
+-t::
+--track::
+	When creating a new branch, set up "upstream" configuration.
+	`-c` is implied. See "--track" in linkgit:git-branch[1] for
+	details.
++
+If no `-c` option is given, the name of the new branch will be derived
+from the remote-tracking branch, by looking at the local part of the
+refspec configured for the corresponding remote, and then stripping
+the initial part up to the "*".  This would tell us to use "hack" as
+the local branch when branching off of "origin/hack" (or
+"remotes/origin/hack", or even "refs/remotes/origin/hack").  If the
+given name has no slash, or the above guessing results in an empty
+name, the guessing is aborted.  You can explicitly give a name with
+`-c` in such a case.
+
+--no-track::
+	Do not set up "upstream" configuration, even if the
+	branch.autoSetupMerge configuration variable is true.
+
+-m::
+--merge::
+	If you have local modifications to one or more files that are
+	different between the current branch and the branch to which
+	you are switching, the command refuses to switch branches in
+	order to preserve your modifications in context.  However,
+	with this option, a three-way merge between the current
+	branch, your working tree contents, and the new branch is
+	done, and you will be on the new branch.
++
+When a merge conflict happens, the index entries for conflicting
+paths are left unmerged, and you need to resolve the conflicts
+and mark the resolved paths with `git add` (or `git rm` if the merge
+should result in deletion of the path).
+
+--conflict=<style>::
+	The same as --merge option above, but changes the way the
+	conflicting hunks are presented, overriding the
+	merge.conflictStyle configuration variable.  Possible values are
+	"merge" (default) and "diff3" (in addition to what is shown by
+	"merge" style, shows the original contents).
+
+--orphan <new_branch>::
+	Create a new 'orphan' branch, named <new_branch>, started from
+	<start_point> and switch to it. See explanation of the same
+	option in linkgit:git-checkout[1] for details.
+
+--ignore-other-worktrees::
+	`git switch` refuses when the wanted ref is already
+	checked out by another worktree. This option makes it check
+	the ref out anyway. In other words, the ref can be held by
+	more than one worktree.
+
+--[no-]recurse-submodules::
+	Using --recurse-submodules will update the content of all initialized
+	submodules according to the commit recorded in the superproject. If
+	local modifications in a submodule would be overwritten the checkout
+	will fail unless `-f` is used. If nothing (or --no-recurse-submodules)
+	is used, the work trees of submodules will not be updated.
+	Just like linkgit:git-submodule[1], this will detach the
+	submodules HEAD.
+
+EXAMPLES
+--------
+
+The following command switches to the "master" branch:
+
+------------
+$ git switch master
+------------
+
+After working in the wrong branch, switching to the correct branch
+would be done using:
+
+------------
+$ git switch mytopic
+------------
+
+However, your "wrong" branch and correct "mytopic" branch may differ
+in files that you have modified locally, in which case the above
+switch would fail like this:
+
+------------
+$ git switch mytopic
+error: You have local changes to 'frotz'; not switching branches.
+------------
+
+You can give the `-m` flag to the command, which would try a three-way
+merge:
+
+------------
+$ git switch -m mytopic
+Auto-merging frotz
+------------
+
+After this three-way merge, the local modifications are _not_
+registered in your index file, so `git diff` would show you what
+changes you made since the tip of the new branch.
+
+To switch back to the previous branch before we switched to mytopic
+(i.e. "master" branch):
+
+------------
+$ git switch -
+------------
+
+You can grow a new branch from any commit. For example, switch to
+"HEAD~3" and create branch "fixup":
+
+------------
+$ git switch -c fixup HEAD~3
+Switched to a new branch 'fixup'
+------------
+
+If you want to start a new branch from a remote branch of the same
+name, use `-g`:
+
+------------
+$ git switch -g new-topic
+Branch 'new-topic' set up to track remote branch 'new-topic' from 'origin'
+Switched to a new branch 'new-topic'
+------------
+
+To check out commit "HEAD~3" for temporary inspection or experiment
+without creating a new branch:
+
+------------
+$ git switch --detach HEAD~3
+HEAD is now at 9fc9555312 Merge branch 'cc/shared-index-permbits'
+------------
+
+If it turns out whatever you have done is worth keeping, you can
+always create a new name for it (without switching away):
+
+------------
+$ git switch -c good-surprises
+------------
+
+SEE ALSO
+--------
+linkgit:git-checkout[1]
+
+GIT
+---
+Part of the linkgit:git[1] suite
diff --git a/Documentation/gitattributes.txt b/Documentation/gitattributes.txt
index b8392fc330..5731caa4c6 100644
--- a/Documentation/gitattributes.txt
+++ b/Documentation/gitattributes.txt
@@ -112,7 +112,8 @@ Checking-out and checking-in
 
 These attributes affect how the contents stored in the
 repository are copied to the working tree files when commands
-such as 'git checkout' and 'git merge' run.  They also affect how
+such as 'git switch', 'git checkout'  and 'git merge' run.
+They also affect how
 Git stores the contents you prepare in the working tree in the
 repository upon 'git add' and 'git commit'.
 
diff --git a/Documentation/githooks.txt b/Documentation/githooks.txt
index 959044347e..e257a7810a 100644
--- a/Documentation/githooks.txt
+++ b/Documentation/githooks.txt
@@ -161,12 +161,13 @@ rebased, and is not set when rebasing the current branch.
 post-checkout
 ~~~~~~~~~~~~~
 
-This hook is invoked when a linkgit:git-checkout[1] is run after having updated the
+This hook is invoked when a linkgit:git-checkout[1] or
+linkgit:git-switch[1] is run after having updated the
 worktree.  The hook is given three parameters: the ref of the previous HEAD,
 the ref of the new HEAD (which may or may not have changed), and a flag
 indicating whether the checkout was a branch checkout (changing branches,
 flag=1) or a file checkout (retrieving a file from the index, flag=0).
-This hook cannot affect the outcome of `git checkout`.
+This hook cannot affect the outcome of `git switch` or `git checkout`.
 
 It is also run after linkgit:git-clone[1], unless the `--no-checkout` (`-n`) option is
 used. The first parameter given to the hook is the null-ref, the second the
@@ -402,7 +403,8 @@ exit with a zero status.
 For example, the hook can simply run `git read-tree -u -m HEAD "$1"`
 in order to emulate `git fetch` that is run in the reverse direction
 with `git push`, as the two-tree form of `git read-tree -u -m` is
-essentially the same as `git checkout` that switches branches while
+essentially the same as `git switch` or `git checkout`
+that switches branches while
 keeping the local changes in the working tree that do not interfere
 with the difference between the branches.
 
diff --git a/Makefile b/Makefile
index 6e8d017e8e..0e5b29390c 100644
--- a/Makefile
+++ b/Makefile
@@ -789,6 +789,7 @@ BUILT_INS += git-merge-subtree$X
 BUILT_INS += git-show$X
 BUILT_INS += git-stage$X
 BUILT_INS += git-status$X
+BUILT_INS += git-switch$X
 BUILT_INS += git-whatchanged$X
 
 # what 'all' will build and 'install' will install in gitexecdir,
diff --git a/builtin.h b/builtin.h
index 6538932e99..c64e44450e 100644
--- a/builtin.h
+++ b/builtin.h
@@ -227,6 +227,7 @@ extern int cmd_show_index(int argc, const char **argv, const char *prefix);
 extern int cmd_status(int argc, const char **argv, const char *prefix);
 extern int cmd_stripspace(int argc, const char **argv, const char *prefix);
 extern int cmd_submodule__helper(int argc, const char **argv, const char *prefix);
+extern int cmd_switch(int argc, const char **argv, const char *prefix);
 extern int cmd_symbolic_ref(int argc, const char **argv, const char *prefix);
 extern int cmd_tag(int argc, const char **argv, const char *prefix);
 extern int cmd_tar_tree(int argc, const char **argv, const char *prefix);
diff --git a/builtin/checkout.c b/builtin/checkout.c
index 8ea1349cce..2ac53b4302 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -33,6 +33,11 @@ static const char * const checkout_usage[] = {
 	NULL,
 };
 
+static const char * const switch_branch_usage[] = {
+	N_("git switch [<options>] [<branch>]"),
+	NULL,
+};
+
 struct checkout_opts {
 	int patch_mode;
 	int quiet;
@@ -1396,33 +1401,25 @@ static struct option *add_checkout_path_options(struct checkout_opts *opts,
 	return newopts;
 }
 
-int cmd_checkout(int argc, const char **argv, const char *prefix)
+static int checkout_main(int argc, const char **argv, const char *prefix,
+			 struct checkout_opts *opts, struct option *options,
+			 const char * const usagestr[])
 {
-	struct checkout_opts real_opts;
-	struct checkout_opts *opts = &real_opts;
 	struct branch_info new_branch_info;
 	int dwim_remotes_matched = 0;
 	int dwim_new_local_branch;
-	struct option *options = NULL;
 
-	memset(opts, 0, sizeof(*opts));
 	memset(&new_branch_info, 0, sizeof(new_branch_info));
 	opts->overwrite_ignore = 1;
 	opts->prefix = prefix;
 	opts->show_progress = -1;
 	opts->overlay_mode = -1;
-	opts->no_dwim_new_local_branch = 0;
 
 	git_config(git_checkout_config, opts);
 
 	opts->track = BRANCH_TRACK_UNSPECIFIED;
 
-	options = parse_options_dup(options);
-	options = add_common_options(opts, options);
-	options = add_switch_branch_options(opts, options);
-	options = add_checkout_path_options(opts, options);
-
-	argc = parse_options(argc, argv, prefix, options, checkout_usage,
+	argc = parse_options(argc, argv, prefix, options, usagestr,
 			     PARSE_OPT_KEEP_DASHDASH);
 
 	dwim_new_local_branch = !opts->no_dwim_new_local_branch;
@@ -1555,3 +1552,42 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 		return checkout_branch(opts, &new_branch_info);
 	}
 }
+
+int cmd_checkout(int argc, const char **argv, const char *prefix)
+{
+	struct checkout_opts opts;
+	struct option *options = NULL;
+	int ret;
+
+	memset(&opts, 0, sizeof(opts));
+	opts.no_dwim_new_local_branch = 0;
+
+	options = parse_options_dup(options);
+	options = add_common_options(&opts, options);
+	options = add_switch_branch_options(&opts, options);
+	options = add_checkout_path_options(&opts, options);
+
+	ret = checkout_main(argc, argv, prefix, &opts,
+			    options, checkout_usage);
+	FREE_AND_NULL(options);
+	return ret;
+}
+
+int cmd_switch(int argc, const char **argv, const char *prefix)
+{
+	struct checkout_opts opts;
+	struct option *options = NULL;
+	int ret;
+
+	memset(&opts, 0, sizeof(opts));
+	opts.no_dwim_new_local_branch = 0;
+
+	options = parse_options_dup(options);
+	options = add_common_options(&opts, options);
+	options = add_switch_branch_options(&opts, options);
+
+	ret = checkout_main(argc, argv, prefix, &opts,
+			    options, switch_branch_usage);
+	FREE_AND_NULL(options);
+	return ret;
+}
diff --git a/command-list.txt b/command-list.txt
index 3a9af104b5..13317f47d4 100644
--- a/command-list.txt
+++ b/command-list.txt
@@ -171,6 +171,7 @@ git-status                              mainporcelain           info
 git-stripspace                          purehelpers
 git-submodule                           mainporcelain
 git-svn                                 foreignscminterface
+git-switch                              mainporcelain           history
 git-symbolic-ref                        plumbingmanipulators
 git-tag                                 mainporcelain           history
 git-unpack-file                         plumbinginterrogators
diff --git a/git.c b/git.c
index 0ce0e13f0f..31b8e8d6a1 100644
--- a/git.c
+++ b/git.c
@@ -558,6 +558,7 @@ static struct cmd_struct commands[] = {
 	{ "status", cmd_status, RUN_SETUP | NEED_WORK_TREE },
 	{ "stripspace", cmd_stripspace },
 	{ "submodule--helper", cmd_submodule__helper, RUN_SETUP | SUPPORT_SUPER_PREFIX | NO_PARSEOPT },
+	{ "switch", cmd_switch, RUN_SETUP | NEED_WORK_TREE },
 	{ "symbolic-ref", cmd_symbolic_ref, RUN_SETUP },
 	{ "tag", cmd_tag, RUN_SETUP | DELAY_PAGER_CONFIG },
 	{ "unpack-file", cmd_unpack_file, RUN_SETUP | NO_PARSEOPT },

diff --git a/Documentation/git-commit.txt b/Documentation/git-commit.txt
index f970a43422..8148ba10b3 100644
--- a/Documentation/git-commit.txt
+++ b/Documentation/git-commit.txt
@@ -17,16 +17,19 @@ SYNOPSIS
 
 DESCRIPTION
 -----------
-Stores the current contents of the index in a new commit along
-with a log message from the user describing the changes.
+Creates a new commit containing the current contents of the index with
+a log message from the user describing the changes. The commit is the
+direct child of the tip of the current branch. The branch is updated
+to point to the new commit (unless no branch is associated with the
+working tree, see "NOTES" section).
 
-The content to be added can be specified in several ways:
+The content to be committed can be specified in several ways:
 
-1. by using 'git add' to incrementally "add" changes to the
-   index before using the 'commit' command (Note: even modified
-   files must be "added");
+1. by using linkgit:git-add[1] to incrementally "add" changes to the
+   index before using the 'commit' command (Note: even modified files
+   must be "added");
 
-2. by using 'git rm' to remove files from the working tree
+2. by using linkgit:git-rm[1] to remove files from the working tree
    and the index, again before using the 'commit' command;
 
 3. by listing files as arguments to the 'commit' command
@@ -349,6 +352,18 @@ changes to tracked files.
 :git-commit: 1
 include::date-formats.txt[]
 
+NOTES
+-----
+If a branch is associated with the working tree, 'HEAD' points to this
+branch. When a new commit is created, the branch is updated to point
+to the new commit. As a result, resolving 'HEAD' still gives the new
+commit.
+
+If no branch is associated with the working tree (i.e. "detached HEAD"
+as described in linkgit:git-checkout[1]), 'HEAD' records the object
+name of the previous commit directly. When a new commit is created, it
+will be updated to point to the new commit.
+
 EXAMPLES
 --------
 When recording your own work, the contents of modified files in

diff --git a/Documentation/git-commit.txt b/Documentation/git-commit.txt
index f970a43422..a85c2c2a4c 100644
--- a/Documentation/git-commit.txt
+++ b/Documentation/git-commit.txt
@@ -17,16 +17,20 @@ SYNOPSIS
 
 DESCRIPTION
 -----------
-Stores the current contents of the index in a new commit along
-with a log message from the user describing the changes.
+Create a new commit containing the current contents of the index and
+the given log message describing the changes. The new commit is a
+direct child of HEAD, usually the tip of the current branch, and the
+branch is updated to point to it (unless no branch is associated with
+the working tree, in which case HEAD is "detached" as described in
+linkgit:git-checkout[1]).
 
-The content to be added can be specified in several ways:
+The content to be committed can be specified in several ways:
 
-1. by using 'git add' to incrementally "add" changes to the
-   index before using the 'commit' command (Note: even modified
-   files must be "added");
+1. by using linkgit:git-add[1] to incrementally "add" changes to the
+   index before using the 'commit' command (Note: even modified files
+   must be "added");
 
-2. by using 'git rm' to remove files from the working tree
+2. by using linkgit:git-rm[1] to remove files from the working tree
    and the index, again before using the 'commit' command;
 
 3. by listing files as arguments to the 'commit' command

diff --git a/builtin/checkout.c b/builtin/checkout.c
index 2ac53b4302..2251883a88 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -1353,14 +1353,10 @@ static struct option *add_common_options(struct checkout_opts *opts,
 	return newopts;
 }
 
-static struct option *add_switch_branch_options(struct checkout_opts *opts,
-						struct option *prevopts)
+static struct option *add_common_switch_branch_options(
+	struct checkout_opts *opts, struct option *prevopts)
 {
 	struct option options[] = {
-		OPT_STRING('b', NULL, &opts->new_branch, N_("branch"),
-			   N_("create and checkout a new branch")),
-		OPT_STRING('B', NULL, &opts->new_branch_force, N_("branch"),
-			   N_("create/reset and checkout a branch")),
 		OPT_BOOL('l', NULL, &opts->new_branch_log, N_("create reflog for new branch")),
 		OPT_BOOL(0, "detach", &opts->force_detach, N_("detach HEAD at named commit")),
 		OPT_SET_INT('t', "track",  &opts->track, N_("set upstream info for new branch"),
@@ -1556,15 +1552,22 @@ static int checkout_main(int argc, const char **argv, const char *prefix,
 int cmd_checkout(int argc, const char **argv, const char *prefix)
 {
 	struct checkout_opts opts;
-	struct option *options = NULL;
+	struct option *options;
+	struct option checkout_options[] = {
+		OPT_STRING('b', NULL, &opts.new_branch, N_("branch"),
+			   N_("create and checkout a new branch")),
+		OPT_STRING('B', NULL, &opts.new_branch_force, N_("branch"),
+			   N_("create/reset and checkout a branch")),
+		OPT_END()
+	};
 	int ret;
 
 	memset(&opts, 0, sizeof(opts));
 	opts.no_dwim_new_local_branch = 0;
 
-	options = parse_options_dup(options);
+	options = parse_options_dup(checkout_options);
 	options = add_common_options(&opts, options);
-	options = add_switch_branch_options(&opts, options);
+	options = add_common_switch_branch_options(&opts, options);
 	options = add_checkout_path_options(&opts, options);
 
 	ret = checkout_main(argc, argv, prefix, &opts,
@@ -1577,14 +1580,21 @@ int cmd_switch(int argc, const char **argv, const char *prefix)
 {
 	struct checkout_opts opts;
 	struct option *options = NULL;
+	struct option switch_options[] = {
+		OPT_STRING('c', "create", &opts.new_branch, N_("branch"),
+			   N_("create and switch to a new branch")),
+		OPT_STRING('C', "force-create", &opts.new_branch_force, N_("branch"),
+			   N_("create/reset and switch to a new branch")),
+		OPT_END()
+	};
 	int ret;
 
 	memset(&opts, 0, sizeof(opts));
 	opts.no_dwim_new_local_branch = 0;
 
-	options = parse_options_dup(options);
+	options = parse_options_dup(switch_options);
 	options = add_common_options(&opts, options);
-	options = add_switch_branch_options(&opts, options);
+	options = add_common_switch_branch_options(&opts, options);
 
 	ret = checkout_main(argc, argv, prefix, &opts,
 			    options, switch_branch_usage);

diff --git a/builtin/checkout.c b/builtin/checkout.c
index 2251883a88..db9a2692db 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -1357,7 +1357,6 @@ static struct option *add_common_switch_branch_options(
 	struct checkout_opts *opts, struct option *prevopts)
 {
 	struct option options[] = {
-		OPT_BOOL('l', NULL, &opts->new_branch_log, N_("create reflog for new branch")),
 		OPT_BOOL(0, "detach", &opts->force_detach, N_("detach HEAD at named commit")),
 		OPT_SET_INT('t', "track",  &opts->track, N_("set upstream info for new branch"),
 			BRANCH_TRACK_EXPLICIT),
@@ -1558,6 +1557,7 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 			   N_("create and checkout a new branch")),
 		OPT_STRING('B', NULL, &opts.new_branch_force, N_("branch"),
 			   N_("create/reset and checkout a branch")),
+		OPT_BOOL('l', NULL, &opts.new_branch_log, N_("create reflog for new branch")),
 		OPT_END()
 	};
 	int ret;

diff --git a/builtin/checkout.c b/builtin/checkout.c
index db9a2692db..7906e07352 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -52,6 +52,7 @@ struct checkout_opts {
 	int count_checkout_paths;
 	int overlay_mode;
 	int no_dwim_new_local_branch;
+	int accept_pathspec;
 
 	/*
 	 * If new checkout options are added, skip_merge_working_tree
@@ -1162,10 +1163,16 @@ static int parse_branchname_arg(int argc, const char **argv,
 	if (!argc)
 		return 0;
 
+	if (!opts->accept_pathspec) {
+		if (argc > 1)
+			die(_("only one reference expected"));
+		has_dash_dash = 1; /* helps disambiguate */
+	}
+
 	arg = argv[0];
 	dash_dash_pos = -1;
 	for (i = 0; i < argc; i++) {
-		if (!strcmp(argv[i], "--")) {
+		if (opts->accept_pathspec && !strcmp(argv[i], "--")) {
 			dash_dash_pos = i;
 			break;
 		}
@@ -1199,11 +1206,12 @@ static int parse_branchname_arg(int argc, const char **argv,
 			recover_with_dwim = 0;
 
 		/*
-		 * Accept "git checkout foo" and "git checkout foo --"
-		 * as candidates for dwim.
+		 * Accept "git checkout foo", "git checkout foo --"
+		 * and "git switch foo" as candidates for dwim.
 		 */
 		if (!(argc == 1 && !has_dash_dash) &&
-		    !(argc == 2 && has_dash_dash))
+		    !(argc == 2 && has_dash_dash) &&
+		    opts->accept_pathspec)
 			recover_with_dwim = 0;
 
 		if (recover_with_dwim) {
@@ -1248,7 +1256,7 @@ static int parse_branchname_arg(int argc, const char **argv,
 		 */
 		if (argc)
 			verify_non_filename(opts->prefix, arg);
-	} else {
+	} else if (opts->accept_pathspec) {
 		argcount++;
 		argv++;
 		argc--;
@@ -1564,6 +1572,7 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 
 	memset(&opts, 0, sizeof(opts));
 	opts.no_dwim_new_local_branch = 0;
+	opts.accept_pathspec = 1;
 
 	options = parse_options_dup(checkout_options);
 	options = add_common_options(&opts, options);
@@ -1591,6 +1600,7 @@ int cmd_switch(int argc, const char **argv, const char *prefix)
 
 	memset(&opts, 0, sizeof(opts));
 	opts.no_dwim_new_local_branch = 0;
+	opts.accept_pathspec = 0;
 
 	options = parse_options_dup(switch_options);
 	options = add_common_options(&opts, options);

diff --git a/builtin/checkout.c b/builtin/checkout.c
index 7906e07352..9a58fccd71 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -53,6 +53,7 @@ struct checkout_opts {
 	int overlay_mode;
 	int no_dwim_new_local_branch;
 	int accept_pathspec;
+	int switch_branch_doing_nothing_is_ok;
 
 	/*
 	 * If new checkout options are added, skip_merge_working_tree
@@ -1319,6 +1320,12 @@ static int checkout_branch(struct checkout_opts *opts,
 		die(_("Cannot switch branch to a non-commit '%s'"),
 		    new_branch_info->name);
 
+	if (!opts->switch_branch_doing_nothing_is_ok &&
+	    !new_branch_info->name &&
+	    !opts->new_branch &&
+	    !opts->force_detach)
+		die(_("nothing to do"));
+
 	if (new_branch_info->path && !opts->force_detach && !opts->new_branch &&
 	    !opts->ignore_other_worktrees) {
 		int flag;
@@ -1572,6 +1579,7 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 
 	memset(&opts, 0, sizeof(opts));
 	opts.no_dwim_new_local_branch = 0;
+	opts.switch_branch_doing_nothing_is_ok = 1;
 	opts.accept_pathspec = 1;
 
 	options = parse_options_dup(checkout_options);
@@ -1601,6 +1609,7 @@ int cmd_switch(int argc, const char **argv, const char *prefix)
 	memset(&opts, 0, sizeof(opts));
 	opts.no_dwim_new_local_branch = 0;
 	opts.accept_pathspec = 0;
+	opts.switch_branch_doing_nothing_is_ok = 0;
 
 	options = parse_options_dup(switch_options);
 	options = add_common_options(&opts, options);

diff --git a/builtin/checkout.c b/builtin/checkout.c
index 9a58fccd71..69df3a1547 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -44,6 +44,7 @@ struct checkout_opts {
 	int merge;
 	int force;
 	int force_detach;
+	int implicit_detach;
 	int writeout_stage;
 	int overwrite_ignore;
 	int ignore_skipworktree;
@@ -1326,6 +1327,14 @@ static int checkout_branch(struct checkout_opts *opts,
 	    !opts->force_detach)
 		die(_("nothing to do"));
 
+	if (!opts->implicit_detach &&
+	    !opts->force_detach &&
+	    !opts->new_branch &&
+	    !opts->new_branch_force &&
+	    new_branch_info->name &&
+	    !new_branch_info->path)
+		die(_("a branch is expected, got %s"), new_branch_info->name);
+
 	if (new_branch_info->path && !opts->force_detach && !opts->new_branch &&
 	    !opts->ignore_other_worktrees) {
 		int flag;
@@ -1581,6 +1590,7 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 	opts.no_dwim_new_local_branch = 0;
 	opts.switch_branch_doing_nothing_is_ok = 1;
 	opts.accept_pathspec = 1;
+	opts.implicit_detach = 1;
 
 	options = parse_options_dup(checkout_options);
 	options = add_common_options(&opts, options);
@@ -1610,6 +1620,7 @@ int cmd_switch(int argc, const char **argv, const char *prefix)
 	opts.no_dwim_new_local_branch = 0;
 	opts.accept_pathspec = 0;
 	opts.switch_branch_doing_nothing_is_ok = 0;
+	opts.implicit_detach = 0;
 
 	options = parse_options_dup(switch_options);
 	options = add_common_options(&opts, options);

diff --git a/builtin/checkout.c b/builtin/checkout.c
index 69df3a1547..49c7ac211e 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -1381,7 +1381,7 @@ static struct option *add_common_switch_branch_options(
 	struct checkout_opts *opts, struct option *prevopts)
 {
 	struct option options[] = {
-		OPT_BOOL(0, "detach", &opts->force_detach, N_("detach HEAD at named commit")),
+		OPT_BOOL('d', "detach", &opts->force_detach, N_("detach HEAD at named commit")),
 		OPT_SET_INT('t', "track",  &opts->track, N_("set upstream info for new branch"),
 			BRANCH_TRACK_EXPLICIT),
 		OPT_STRING(0, "orphan", &opts->new_orphan_branch, N_("new-branch"), N_("new unparented branch")),

Documentation/git-checkout.txt, builtin/checkout.c

diff --git a/Documentation/git-checkout.txt b/Documentation/git-checkout.txt
index 31c6cbef19..bcb7822c27 100644
--- a/Documentation/git-checkout.txt
+++ b/Documentation/git-checkout.txt
@@ -31,22 +31,13 @@ branch.
 	<branch>.
 +
 If <branch> is not found but there does exist a tracking branch in
-exactly one remote (call it <remote>) with a matching name, treat as
-equivalent to
+exactly one remote (call it <remote>) with a matching name and
+--no-guess is not specified, treat as equivalent to
 +
 ------------
 $ git checkout -b <branch> --track <remote>/<branch>
 ------------
 +
-If the branch exists in multiple remotes and one of them is named by
-the `checkout.defaultRemote` configuration variable, we'll use that
-one for the purposes of disambiguation, even if the `<branch>` isn't
-unique across all remotes. Set it to
-e.g. `checkout.defaultRemote=origin` to always checkout remote
-branches from there if `<branch>` is ambiguous but exists on the
-'origin' remote. See also `checkout.defaultRemote` in
-linkgit:git-config[1].
-+
 You could omit <branch>, in which case the command degenerates to
 "check out the current branch", which is a glorified no-op with
 rather expensive side-effects to show only the tracking information,
@@ -182,6 +173,26 @@ explicitly give a name with `-b` in such a case.
 	Do not set up "upstream" configuration, even if the
 	branch.autoSetupMerge configuration variable is true.
 
+--[no-]guess::
+	If <branch> is not found but there does exist a tracking
+	branch in exactly one remote (call it <remote>) with a
+	matching name, treat as equivalent to
++
+------------
+$ git checkout -b <branch> --track <remote>/<branch>
+------------
++
+If the branch exists in multiple remotes and one of them is named by
+the `checkout.defaultRemote` configuration variable, we'll use that
+one for the purposes of disambiguation, even if the `<branch>` isn't
+unique across all remotes. Set it to
+e.g. `checkout.defaultRemote=origin` to always checkout remote
+branches from there if `<branch>` is ambiguous but exists on the
+'origin' remote. See also `checkout.defaultRemote` in
+linkgit:git-config[1].
++
+Use `--no-guess` to disable this.
+
 -l::
 	Create the new branch's reflog; see linkgit:git-branch[1] for
 	details.
@@ -284,10 +295,6 @@ Note that this option uses the no overlay mode by default (see also
 	Just like linkgit:git-submodule[1], this will detach the
 	submodules HEAD.
 
---no-guess::
-	Do not attempt to create a branch if a remote tracking branch
-	of the same name exists.
-
 --[no-]overlay::
 	In the default overlay mode, `git checkout` never
 	removes files from the index or the working tree.  When
diff --git a/builtin/checkout.c b/builtin/checkout.c
index 49c7ac211e..cdd07f6aba 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -52,7 +52,7 @@ struct checkout_opts {
 	int show_progress;
 	int count_checkout_paths;
 	int overlay_mode;
-	int no_dwim_new_local_branch;
+	int dwim_new_local_branch;
 	int accept_pathspec;
 	int switch_branch_doing_nothing_is_ok;
 
@@ -1388,8 +1388,6 @@ static struct option *add_common_switch_branch_options(
 		OPT_BOOL_F(0, "overwrite-ignore", &opts->overwrite_ignore,
 			   N_("update ignored files (default)"),
 			   PARSE_OPT_NOCOMPLETE),
-		OPT_BOOL(0, "no-guess", &opts->no_dwim_new_local_branch,
-			 N_("second guess 'git checkout <no-such-branch>'")),
 		OPT_BOOL(0, "ignore-other-worktrees", &opts->ignore_other_worktrees,
 			 N_("do not check if another worktree is holding the given ref")),
 		OPT_END()
@@ -1426,7 +1424,6 @@ static int checkout_main(int argc, const char **argv, const char *prefix,
 {
 	struct branch_info new_branch_info;
 	int dwim_remotes_matched = 0;
-	int dwim_new_local_branch;
 
 	memset(&new_branch_info, 0, sizeof(new_branch_info));
 	opts->overwrite_ignore = 1;
@@ -1441,7 +1438,6 @@ static int checkout_main(int argc, const char **argv, const char *prefix,
 	argc = parse_options(argc, argv, prefix, options, usagestr,
 			     PARSE_OPT_KEEP_DASHDASH);
 
-	dwim_new_local_branch = !opts->no_dwim_new_local_branch;
 	if (opts->show_progress < 0) {
 		if (opts->quiet)
 			opts->show_progress = 0;
@@ -1501,7 +1497,7 @@ static int checkout_main(int argc, const char **argv, const char *prefix,
 		struct object_id rev;
 		int dwim_ok =
 			!opts->patch_mode &&
-			dwim_new_local_branch &&
+			opts->dwim_new_local_branch &&
 			opts->track == BRANCH_TRACK_UNSPECIFIED &&
 			!opts->new_branch;
 		int n = parse_branchname_arg(argc, argv, dwim_ok,
@@ -1582,12 +1578,14 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 		OPT_STRING('B', NULL, &opts.new_branch_force, N_("branch"),
 			   N_("create/reset and checkout a branch")),
 		OPT_BOOL('l', NULL, &opts.new_branch_log, N_("create reflog for new branch")),
+		OPT_BOOL(0, "guess", &opts.dwim_new_local_branch,
+			 N_("second guess 'git checkout <no-such-branch>' (default)")),
 		OPT_END()
 	};
 	int ret;
 
 	memset(&opts, 0, sizeof(opts));
-	opts.no_dwim_new_local_branch = 0;
+	opts.dwim_new_local_branch = 1;
 	opts.switch_branch_doing_nothing_is_ok = 1;
 	opts.accept_pathspec = 1;
 	opts.implicit_detach = 1;
@@ -1612,12 +1610,14 @@ int cmd_switch(int argc, const char **argv, const char *prefix)
 			   N_("create and switch to a new branch")),
 		OPT_STRING('C', "force-create", &opts.new_branch_force, N_("branch"),
 			   N_("create/reset and switch to a new branch")),
+		OPT_BOOL('g', "guess", &opts.dwim_new_local_branch,
+			 N_("second guess 'git switch <no-such-branch>'")),
 		OPT_END()
 	};
 	int ret;
 
 	memset(&opts, 0, sizeof(opts));
-	opts.no_dwim_new_local_branch = 0;
+	opts.dwim_new_local_branch = 0;
 	opts.accept_pathspec = 0;
 	opts.switch_branch_doing_nothing_is_ok = 0;
 	opts.implicit_detach = 0;

Documentation/config/checkout.txt, builtin/checkout.c, t/t1090-sparse-checkout-scope.sh

diff --git a/Documentation/config/checkout.txt b/Documentation/config/checkout.txt
index fc211eca58..2fe24049fe 100644
--- a/Documentation/config/checkout.txt
+++ b/Documentation/config/checkout.txt
@@ -17,14 +17,6 @@ and by linkgit:git-worktree[1] when 'git worktree add' refers to a
 remote branch. This setting might be used for other checkout-like
 commands or functionality in the future.
 
-checkout.optimizeNewBranch::
-	Optimizes the performance of "git checkout -b <new_branch>" when
-	using sparse-checkout.  When set to true, git will not update the
-	repo based on the current sparse-checkout settings.  This means it
-	will not update the skip-worktree bit in the index nor add/remove
-	files in the working directory to reflect the current sparse checkout
-	settings nor will it show the local changes.
-
 checkout.overlayMode::
 	In the default overlay mode, `git checkout` never
 	removes files from the index or the working tree.  When
diff --git a/builtin/checkout.c b/builtin/checkout.c
index cdd07f6aba..8b4aabd6db 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -25,8 +25,6 @@
 #include "submodule.h"
 #include "advice.h"
 
-static int checkout_optimize_new_branch;
-
 static const char * const checkout_usage[] = {
 	N_("git checkout [<options>] <branch>"),
 	N_("git checkout [<options>] [<branch>] -- <file>..."),
@@ -55,11 +53,7 @@ struct checkout_opts {
 	int dwim_new_local_branch;
 	int accept_pathspec;
 	int switch_branch_doing_nothing_is_ok;
-
-	/*
-	 * If new checkout options are added, skip_merge_working_tree
-	 * should be updated accordingly.
-	 */
+	int only_merge_on_switching_branches;
 
 	const char *new_branch;
 	const char *new_branch_force;
@@ -556,104 +550,6 @@ static void setup_branch_path(struct branch_info *branch)
 	branch->path = strbuf_detach(&buf, NULL);
 }
 
-/*
- * Skip merging the trees, updating the index and working directory if and
- * only if we are creating a new branch via "git checkout -b <new_branch>."
- */
-static int skip_merge_working_tree(const struct checkout_opts *opts,
-	const struct branch_info *old_branch_info,
-	const struct branch_info *new_branch_info)
-{
-	/*
-	 * Do the merge if sparse checkout is on and the user has not opted in
-	 * to the optimized behavior
-	 */
-	if (core_apply_sparse_checkout && !checkout_optimize_new_branch)
-		return 0;
-
-	/*
-	 * We must do the merge if we are actually moving to a new commit.
-	 */
-	if (!old_branch_info->commit || !new_branch_info->commit ||
-		!oideq(&old_branch_info->commit->object.oid,
-		       &new_branch_info->commit->object.oid))
-		return 0;
-
-	/*
-	 * opts->patch_mode cannot be used with switching branches so is
-	 * not tested here
-	 */
-
-	/*
-	 * opts->quiet only impacts output so doesn't require a merge
-	 */
-
-	/*
-	 * Honor the explicit request for a three-way merge or to throw away
-	 * local changes
-	 */
-	if (opts->merge || opts->force)
-		return 0;
-
-	/*
-	 * --detach is documented as "updating the index and the files in the
-	 * working tree" but this optimization skips those steps so fall through
-	 * to the regular code path.
-	 */
-	if (opts->force_detach)
-		return 0;
-
-	/*
-	 * opts->writeout_stage cannot be used with switching branches so is
-	 * not tested here
-	 */
-
-	/*
-	 * Honor the explicit ignore requests
-	 */
-	if (!opts->overwrite_ignore || opts->ignore_skipworktree ||
-		opts->ignore_other_worktrees)
-		return 0;
-
-	/*
-	 * opts->show_progress only impacts output so doesn't require a merge
-	 */
-
-	/*
-	 * opts->overlay_mode cannot be used with switching branches so is
-	 * not tested here
-	 */
-
-	/*
-	 * If we aren't creating a new branch any changes or updates will
-	 * happen in the existing branch.  Since that could only be updating
-	 * the index and working directory, we don't want to skip those steps
-	 * or we've defeated any purpose in running the command.
-	 */
-	if (!opts->new_branch)
-		return 0;
-
-	/*
-	 * new_branch_force is defined to "create/reset and checkout a branch"
-	 * so needs to go through the merge to do the reset
-	 */
-	if (opts->new_branch_force)
-		return 0;
-
-	/*
-	 * A new orphaned branch requrires the index and the working tree to be
-	 * adjusted to <start_point>
-	 */
-	if (opts->new_orphan_branch)
-		return 0;
-
-	/*
-	 * Remaining variables are not checkout options but used to track state
-	 */
-
-	return 1;
-}
-
 static int merge_working_tree(const struct checkout_opts *opts,
 			      struct branch_info *old_branch_info,
 			      struct branch_info *new_branch_info,
@@ -1011,6 +907,8 @@ static int switch_branches(const struct checkout_opts *opts,
 	void *path_to_free;
 	struct object_id rev;
 	int flag, writeout_error = 0;
+	int do_merge = 1;
+
 	memset(&old_branch_info, 0, sizeof(old_branch_info));
 	old_branch_info.path = path_to_free = resolve_refdup("HEAD", 0, &rev, &flag);
 	if (old_branch_info.path)
@@ -1027,16 +925,12 @@ static int switch_branches(const struct checkout_opts *opts,
 		if (!new_branch_info->commit)
 			die(_("You are on a branch yet to be born"));
 		parse_commit_or_die(new_branch_info->commit);
+
+		if (opts->only_merge_on_switching_branches)
+			do_merge = 0;
 	}
 
-	/* optimize the "checkout -b <new_branch> path */
-	if (skip_merge_working_tree(opts, &old_branch_info, new_branch_info)) {
-		if (!checkout_optimize_new_branch && !opts->quiet) {
-			if (read_cache_preload(NULL) < 0)
-				return error(_("index file corrupt"));
-			show_local_changes(&new_branch_info->commit->object, &opts->diff_options);
-		}
-	} else {
+	if (do_merge) {
 		ret = merge_working_tree(opts, &old_branch_info, new_branch_info, &writeout_error);
 		if (ret) {
 			free(path_to_free);
@@ -1058,11 +952,6 @@ static int git_checkout_config(const char *var, const char *value, void *cb)
 {
 	struct checkout_opts *opts = cb;
 
-	if (!strcmp(var, "checkout.optimizenewbranch")) {
-		checkout_optimize_new_branch = git_config_bool(var, value);
-		return 0;
-	}
-
 	if (!strcmp(var, "checkout.overlaymode")) {
 		opts->overlay_mode = git_config_bool(var, value);
 		return 0;
@@ -1587,6 +1476,7 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 	memset(&opts, 0, sizeof(opts));
 	opts.dwim_new_local_branch = 1;
 	opts.switch_branch_doing_nothing_is_ok = 1;
+	opts.only_merge_on_switching_branches = 0;
 	opts.accept_pathspec = 1;
 	opts.implicit_detach = 1;
 
@@ -1620,6 +1510,7 @@ int cmd_switch(int argc, const char **argv, const char *prefix)
 	opts.dwim_new_local_branch = 0;
 	opts.accept_pathspec = 0;
 	opts.switch_branch_doing_nothing_is_ok = 0;
+	opts.only_merge_on_switching_branches = 1;
 	opts.implicit_detach = 0;
 
 	options = parse_options_dup(switch_options);
diff --git a/t/t1090-sparse-checkout-scope.sh b/t/t1090-sparse-checkout-scope.sh
index 090b7fc3d3..40cc004326 100755
--- a/t/t1090-sparse-checkout-scope.sh
+++ b/t/t1090-sparse-checkout-scope.sh
@@ -31,20 +31,6 @@ test_expect_success 'perform sparse checkout of master' '
 	test_path_is_file c
 '
 
-test_expect_success 'checkout -b checkout.optimizeNewBranch interaction' '
-	cp .git/info/sparse-checkout .git/info/sparse-checkout.bak &&
-	test_when_finished "
-		mv -f .git/info/sparse-checkout.bak .git/info/sparse-checkout
-		git checkout master
-	" &&
-	echo "/b" >>.git/info/sparse-checkout &&
-	test "$(git ls-files -t b)" = "S b" &&
-	git -c checkout.optimizeNewBranch=true checkout -b fast &&
-	test "$(git ls-files -t b)" = "S b" &&
-	git checkout -b slow &&
-	test "$(git ls-files -t b)" = "H b"
-'
-
 test_expect_success 'merge feature branch into sparse checkout of master' '
 	git merge feature &&
 	test_path_is_file a &&

diff --git a/t/t2060-switch.sh b/t/t2060-switch.sh
new file mode 100755
index 0000000000..252f78c79e
--- /dev/null
+++ b/t/t2060-switch.sh
@@ -0,0 +1,91 @@
+#!/bin/sh
+
+test_description='switch basic functionality'
+
+. ./test-lib.sh
+
+test_expect_success 'setup' '
+	test_commit first &&
+	git branch first-branch &&
+	test_commit second &&
+	test_commit third &&
+	git remote add origin nohost:/nopath &&
+	git update-ref refs/remotes/origin/foo first-branch
+'
+
+test_expect_success 'switch branch no arguments' '
+	test_must_fail git switch
+'
+
+test_expect_success 'switch branch' '
+	git switch first-branch &&
+	test_path_is_missing second.t
+'
+
+test_expect_success 'switch to a commit' '
+	test_must_fail git switch master^{commit}
+'
+
+test_expect_success 'switch and detach' '
+	test_when_finished git switch master &&
+	git switch --detach master^{commit} &&
+	test_must_fail git symbolic-ref HEAD
+'
+
+test_expect_success 'switch and detach current branch' '
+	test_when_finished git switch master &&
+	git switch master &&
+	git switch --detach &&
+	test_must_fail git symbolic-ref HEAD
+'
+
+test_expect_success 'switch and create branch' '
+	test_when_finished git switch master &&
+	git switch -c temp master^ &&
+	git rev-parse master^ >expected &&
+	git rev-parse refs/heads/temp >actual &&
+	test_cmp expected actual &&
+	echo refs/heads/temp >expected-branch &&
+	git symbolic-ref HEAD >actual-branch &&
+	test_cmp expected-branch actual-branch
+'
+
+test_expect_success 'force create branch from HEAD' '
+	test_when_finished git switch master &&
+	git switch --detach master &&
+	git switch -C temp &&
+	git rev-parse master >expected &&
+	git rev-parse refs/heads/temp >actual &&
+	test_cmp expected actual &&
+	echo refs/heads/temp >expected-branch &&
+	git symbolic-ref HEAD >actual-branch &&
+	test_cmp expected-branch actual-branch
+'
+
+test_expect_success 'new orphan branch' '
+	test_when_finished git switch master &&
+	git switch --orphan new-orphan master^ &&
+	test_commit orphan &&
+	git cat-file commit refs/heads/new-orphan >commit &&
+	! grep ^parent commit
+'
+
+test_expect_success 'switching ignores file of same branch name' '
+	test_when_finished git switch master &&
+	: >first-branch &&
+	git switch first-branch &&
+	echo refs/heads/first-branch >expected &&
+	git symbolic-ref HEAD >actual &&
+	test_commit expected actual
+'
+
+test_expect_success 'guess and create branch ' '
+	test_when_finished git switch master &&
+	test_must_fail git switch foo &&
+	git switch --guess foo &&
+	echo refs/heads/foo >expected &&
+	git symbolic-ref HEAD >actual &&
+	test_cmp expected actual
+'
+
+test_done

diff --git a/contrib/completion/git-completion.bash b/contrib/completion/git-completion.bash
index 499e56f83d..891abb72d7 100644
--- a/contrib/completion/git-completion.bash
+++ b/contrib/completion/git-completion.bash
@@ -2126,6 +2126,32 @@ _git_status ()
 	__git_complete_index_file "$complete_opt"
 }
 
+_git_switch ()
+{
+	case "$cur" in
+	--conflict=*)
+		__gitcomp "diff3 merge" "" "${cur##--conflict=}"
+		;;
+	--*)
+		__gitcomp_builtin switch
+		;;
+	*)
+		# check if ---guess was specified to enable DWIM mode
+		local track_opt= only_local_ref=n
+		if [ -n "$(__git_find_on_cmdline "-g --guess")" ]; then
+			track_opt='--track'
+		elif [ -z "$(__git_find_on_cmdline "-d --detach")" ]; then
+			only_local_ref=y
+		fi
+		if [ $only_local_ref = y ]; then
+			__gitcomp_direct "$(__git_heads "" "$cur" " ")"
+		else
+			__git_complete_refs $track_opt
+		fi
+		;;
+	esac
+}
+
 __git_config_get_set_variables ()
 {
 	local prevword word config_file= c=$cword

Documentation/git-branch.txt, Documentation/git-check-ref-format.txt, Documentation/git-format-patch.txt, Documentation/git-merge-base.txt, Documentation/git-rebase.txt, Documentation/git-remote.txt, Documentation/git-rerere.txt, Documentation/git-reset.txt, Documentation/git-stash.txt, Documentation/gitcore-tutorial.txt, Documentation/giteveryday.txt, Documentation/gittutorial.txt, Documentation/revisions.txt, Documentation/user-manual.txt, advice.c, builtin/clone.c, sha1-name.c, t/t2020-checkout-detach.sh

diff --git a/Documentation/git-branch.txt b/Documentation/git-branch.txt
index bf5316ffa9..94c1f24414 100644
--- a/Documentation/git-branch.txt
+++ b/Documentation/git-branch.txt
@@ -48,7 +48,7 @@ The command's second form creates a new branch head named <branchname>
 which points to the current `HEAD`, or <start-point> if given.
 
 Note that this will create the new branch, but it will not switch the
-working tree to it; use "git checkout <newbranch>" to switch to the
+working tree to it; use "git switch <newbranch>" to switch to the
 new branch.
 
 When a local branch is started off a remote-tracking branch, Git sets up the
@@ -194,7 +194,7 @@ This option is only applicable in non-verbose mode.
 +
 This behavior is the default when the start point is a remote-tracking branch.
 Set the branch.autoSetupMerge configuration variable to `false` if you
-want `git checkout` and `git branch` to always behave as if `--no-track`
+want `git switch`, `git checkout` and `git branch` to always behave as if `--no-track`
 were given. Set it to `always` if you want this behavior when the
 start-point is either a local or remote-tracking branch.
 
@@ -293,7 +293,7 @@ Start development from a known tag::
 $ git clone git://git.kernel.org/pub/scm/.../linux-2.6 my2.6
 $ cd my2.6
 $ git branch my2.6.14 v2.6.14   <1>
-$ git checkout my2.6.14
+$ git switch my2.6.14
 ------------
 +
 <1> This step and the next one could be combined into a single step with
@@ -319,7 +319,7 @@ NOTES
 -----
 
 If you are creating a branch that you want to checkout immediately, it is
-easier to use the git checkout command with its `-b` option to create
+easier to use the "git switch" command with its `-c` option to create
 a branch and check it out with a single command.
 
 The options `--contains`, `--no-contains`, `--merged` and `--no-merged`
diff --git a/Documentation/git-check-ref-format.txt b/Documentation/git-check-ref-format.txt
index d9de992585..ee6a4144fb 100644
--- a/Documentation/git-check-ref-format.txt
+++ b/Documentation/git-check-ref-format.txt
@@ -88,7 +88,8 @@ but it is explicitly forbidden at the beginning of a branch name).
 When run with `--branch` option in a repository, the input is first
 expanded for the ``previous checkout syntax''
 `@{-n}`.  For example, `@{-1}` is a way to refer the last thing that
-was checked out using "git checkout" operation. This option should be
+was checked out using "git switch" or "git checkout" operation.
+This option should be
 used by porcelains to accept this syntax anywhere a branch name is
 expected, so they can act as if you typed the branch name. As an
 exception note that, the ``previous checkout operation'' might result
diff --git a/Documentation/git-format-patch.txt b/Documentation/git-format-patch.txt
index 27304428a1..3d42853529 100644
--- a/Documentation/git-format-patch.txt
+++ b/Documentation/git-format-patch.txt
@@ -421,7 +421,7 @@ One way to test if your MUA is set up correctly is:
 * Apply it:
 
     $ git fetch <project> master:test-apply
-    $ git checkout test-apply
+    $ git switch test-apply
     $ git reset --hard
     $ git am a.patch
 
diff --git a/Documentation/git-merge-base.txt b/Documentation/git-merge-base.txt
index 9f07f4f6ed..261d5c1164 100644
--- a/Documentation/git-merge-base.txt
+++ b/Documentation/git-merge-base.txt
@@ -149,7 +149,7 @@ instead.
 Discussion on fork-point mode
 -----------------------------
 
-After working on the `topic` branch created with `git checkout -b
+After working on the `topic` branch created with `git switch -c
 topic origin/master`, the history of remote-tracking branch
 `origin/master` may have been rewound and rebuilt, leading to a
 history of this shape:
diff --git a/Documentation/git-rebase.txt b/Documentation/git-rebase.txt
index 4dd5853d6e..420777c10b 100644
--- a/Documentation/git-rebase.txt
+++ b/Documentation/git-rebase.txt
@@ -17,7 +17,7 @@ SYNOPSIS
 DESCRIPTION
 -----------
 If <branch> is specified, 'git rebase' will perform an automatic
-`git checkout <branch>` before doing anything else.  Otherwise
+`git switch <branch>` before doing anything else.  Otherwise
 it remains on the current branch.
 
 If <upstream> is not specified, the upstream configured in
diff --git a/Documentation/git-remote.txt b/Documentation/git-remote.txt
index 0cad37fb81..9659abbf8e 100644
--- a/Documentation/git-remote.txt
+++ b/Documentation/git-remote.txt
@@ -230,7 +230,7 @@ $ git branch -r
   staging/master
   staging/staging-linus
   staging/staging-next
-$ git checkout -b staging staging/master
+$ git switch -c staging staging/master
 ...
 ------------
 
diff --git a/Documentation/git-rerere.txt b/Documentation/git-rerere.txt
index df310d2a58..fe4434ad9d 100644
--- a/Documentation/git-rerere.txt
+++ b/Documentation/git-rerere.txt
@@ -91,7 +91,7 @@ For such a test, you need to merge master and topic somehow.
 One way to do it is to pull master into the topic branch:
 
 ------------
-	$ git checkout topic
+	$ git switch topic
 	$ git merge master
 
               o---*---o---+ topic
@@ -113,10 +113,10 @@ the upstream might have been advanced since the test merge `+`,
 in which case the final commit graph would look like this:
 
 ------------
-	$ git checkout topic
+	$ git switch topic
 	$ git merge master
 	$ ... work on both topic and master branches
-	$ git checkout master
+	$ git switch master
 	$ git merge topic
 
               o---*---o---+---o---o topic
@@ -136,11 +136,11 @@ merges, you could blow away the test merge, and keep building on
 top of the tip before the test merge:
 
 ------------
-	$ git checkout topic
+	$ git switch topic
 	$ git merge master
 	$ git reset --hard HEAD^ ;# rewind the test merge
 	$ ... work on both topic and master branches
-	$ git checkout master
+	$ git switch master
 	$ git merge topic
 
               o---*---o-------o---o topic
diff --git a/Documentation/git-reset.txt b/Documentation/git-reset.txt
index 9f69ae8b69..020ba838c9 100644
--- a/Documentation/git-reset.txt
+++ b/Documentation/git-reset.txt
@@ -149,9 +149,9 @@ See also the `--amend` option to linkgit:git-commit[1].
 Undo a commit, making it a topic branch::
 +
 ------------
-$ git branch topic/wip     <1>
-$ git reset --hard HEAD~3  <2>
-$ git checkout topic/wip   <3>
+$ git branch topic/wip          <1>
+$ git reset --hard HEAD~3       <2>
+$ git switch topic/wip          <3>
 ------------
 +
 <1> You have made some commits, but realize they were premature
@@ -232,13 +232,13 @@ working tree are not in any shape to be committed yet, but you
 need to get to the other branch for a quick bugfix.
 +
 ------------
-$ git checkout feature ;# you were working in "feature" branch and
-$ work work work       ;# got interrupted
+$ git switch feature  ;# you were working in "feature" branch and
+$ work work work      ;# got interrupted
 $ git commit -a -m "snapshot WIP"                 <1>
-$ git checkout master
+$ git switch master
 $ fix fix fix
 $ git commit ;# commit with real log
-$ git checkout feature
+$ git switch feature
 $ git reset --soft HEAD^ ;# go back to WIP state  <2>
 $ git reset                                       <3>
 ------------
@@ -279,18 +279,18 @@ reset it while keeping the changes in your working tree.
 +
 ------------
 $ git tag start
-$ git checkout -b branch1
+$ git switch -c branch1
 $ edit
 $ git commit ...                            <1>
 $ edit
-$ git checkout -b branch2                   <2>
+$ git switch -c branch2                     <2>
 $ git reset --keep start                    <3>
 ------------
 +
 <1> This commits your first edits in `branch1`.
 <2> In the ideal world, you could have realized that the earlier
     commit did not belong to the new topic when you created and switched
-    to `branch2` (i.e. `git checkout -b branch2 start`), but nobody is
+    to `branch2` (i.e. `git switch -c branch2 start`), but nobody is
     perfect.
 <3> But you can use `reset --keep` to remove the unwanted commit after
     you switched to `branch2`.
diff --git a/Documentation/git-stash.txt b/Documentation/git-stash.txt
index 7ef8c47911..ebb6282db3 100644
--- a/Documentation/git-stash.txt
+++ b/Documentation/git-stash.txt
@@ -235,12 +235,12 @@ return to your original branch to make the emergency fix, like this:
 +
 ----------------------------------------------------------------
 # ... hack hack hack ...
-$ git checkout -b my_wip
+$ git switch -c my_wip
 $ git commit -a -m "WIP"
-$ git checkout master
+$ git switch master
 $ edit emergency fix
 $ git commit -a -m "Fix in a hurry"
-$ git checkout my_wip
+$ git switch my_wip
 $ git reset --soft HEAD^
 # ... continue hacking ...
 ----------------------------------------------------------------
@@ -293,7 +293,8 @@ SEE ALSO
 linkgit:git-checkout[1],
 linkgit:git-commit[1],
 linkgit:git-reflog[1],
-linkgit:git-reset[1]
+linkgit:git-reset[1],
+linkgit:git-switch[1]
 
 GIT
 ---
diff --git a/Documentation/gitcore-tutorial.txt b/Documentation/gitcore-tutorial.txt
index e29a9effcc..6bd0f192cc 100644
--- a/Documentation/gitcore-tutorial.txt
+++ b/Documentation/gitcore-tutorial.txt
@@ -741,7 +741,7 @@ used earlier, and create a branch in it. You do that by simply just
 saying that you want to check out a new branch:
 
 ------------
-$ git checkout -b mybranch
+$ git switch -c mybranch
 ------------
 
 will create a new branch based at the current `HEAD` position, and switch
@@ -755,7 +755,7 @@ just telling 'git checkout' what the base of the checkout would be.
 In other words, if you have an earlier tag or branch, you'd just do
 
 ------------
-$ git checkout -b mybranch earlier-commit
+$ git switch -c mybranch earlier-commit
 ------------
 
 and it would create the new branch `mybranch` at the earlier commit,
@@ -765,7 +765,7 @@ and check out the state at that time.
 You can always just jump back to your original `master` branch by doing
 
 ------------
-$ git checkout master
+$ git switch master
 ------------
 
 (or any other branch-name, for that matter) and if you forget which
@@ -794,7 +794,7 @@ $ git branch <branchname> [startingpoint]
 
 which will simply _create_ the branch, but will not do anything further.
 You can then later -- once you decide that you want to actually develop
-on that branch -- switch to that branch with a regular 'git checkout'
+on that branch -- switch to that branch with a regular 'git switch'
 with the branchname as the argument.
 
 
@@ -808,7 +808,7 @@ being the same as the original `master` branch, let's make sure we're in
 that branch, and do some work there.
 
 ------------------------------------------------
-$ git checkout mybranch
+$ git switch mybranch
 $ echo "Work, work, work" >>hello
 $ git commit -m "Some work." -i hello
 ------------------------------------------------
@@ -825,7 +825,7 @@ does some work in the original branch, and simulate that by going back
 to the master branch, and editing the same file differently there:
 
 ------------
-$ git checkout master
+$ git switch master
 ------------
 
 Here, take a moment to look at the contents of `hello`, and notice how they
@@ -958,7 +958,7 @@ to the `master` branch. Let's go back to `mybranch`, and run
 'git merge' to get the "upstream changes" back to your branch.
 
 ------------
-$ git checkout mybranch
+$ git switch mybranch
 $ git merge -m "Merge upstream changes." master
 ------------
 
@@ -1133,9 +1133,9 @@ Remember, before running 'git merge', our `master` head was at
 work." commit.
 
 ------------
-$ git checkout mybranch
+$ git switch mybranch
 $ git reset --hard master^2
-$ git checkout master
+$ git switch master
 $ git reset --hard master^
 ------------
 
diff --git a/Documentation/giteveryday.txt b/Documentation/giteveryday.txt
index 9f2528fc8c..38015026bb 100644
--- a/Documentation/giteveryday.txt
+++ b/Documentation/giteveryday.txt
@@ -41,7 +41,7 @@ following commands.
 
   * linkgit:git-log[1] to see what happened.
 
-  * linkgit:git-checkout[1] and linkgit:git-branch[1] to switch
+  * linkgit:git-switch[1] and linkgit:git-branch[1] to switch
     branches.
 
   * linkgit:git-add[1] to manage the index file.
@@ -80,7 +80,7 @@ $ git tag v2.43 <2>
 Create a topic branch and develop.::
 +
 ------------
-$ git checkout -b alsa-audio <1>
+$ git switch -c alsa-audio <1>
 $ edit/compile/test
 $ git checkout -- curses/ux_audio_oss.c <2>
 $ git add curses/ux_audio_alsa.c <3>
@@ -90,7 +90,7 @@ $ git commit -a -s <5>
 $ edit/compile/test
 $ git diff HEAD^ <6>
 $ git commit -a --amend <7>
-$ git checkout master <8>
+$ git switch master <8>
 $ git merge alsa-audio <9>
 $ git log --since='3 days ago' <10>
 $ git log v2.43.. curses/ <11>
@@ -148,11 +148,11 @@ Clone the upstream and work on it.  Feed changes to upstream.::
 ------------
 $ git clone git://git.kernel.org/pub/scm/.../torvalds/linux-2.6 my2.6
 $ cd my2.6
-$ git checkout -b mine master <1>
+$ git switch -c mine master <1>
 $ edit/compile/test; git commit -a -s <2>
 $ git format-patch master <3>
 $ git send-email --to="person <email@example.com>" 00*.patch <4>
-$ git checkout master <5>
+$ git switch master <5>
 $ git pull <6>
 $ git log -p ORIG_HEAD.. arch/i386 include/asm-i386 <7>
 $ git ls-remote --heads http://git.kernel.org/.../jgarzik/libata-dev.git <8>
@@ -194,7 +194,7 @@ satellite$ edit/compile/test/commit
 satellite$ git push origin <4>
 
 mothership$ cd frotz
-mothership$ git checkout master
+mothership$ git switch master
 mothership$ git merge satellite/master <5>
 ------------
 +
@@ -216,7 +216,7 @@ machine into the master branch.
 Branch off of a specific tag.::
 +
 ------------
-$ git checkout -b private2.6.14 v2.6.14 <1>
+$ git switch -c private2.6.14 v2.6.14 <1>
 $ edit/compile/test; git commit -a
 $ git checkout master
 $ git cherry-pick v2.6.14..private2.6.14 <2>
@@ -274,14 +274,14 @@ $ mailx <3>
 & s 2 3 4 5 ./+to-apply
 & s 7 8 ./+hold-linus
 & q
-$ git checkout -b topic/one master
+$ git switch -c topic/one master
 $ git am -3 -i -s ./+to-apply <4>
 $ compile/test
-$ git checkout -b hold/linus && git am -3 -i -s ./+hold-linus <5>
-$ git checkout topic/one && git rebase master <6>
-$ git checkout pu && git reset --hard next <7>
+$ git switch -c hold/linus && git am -3 -i -s ./+hold-linus <5>
+$ git switch topic/one && git rebase master <6>
+$ git switch pu && git reset --hard next <7>
 $ git merge topic/one topic/two && git merge hold/linus <8>
-$ git checkout maint
+$ git switch maint
 $ git cherry-pick master~4 <9>
 $ compile/test
 $ git tag -s -m "GIT 0.99.9x" v0.99.9x <10>
diff --git a/Documentation/gittutorial.txt b/Documentation/gittutorial.txt
index 242de31cb6..e6ad6b5f8d 100644
--- a/Documentation/gittutorial.txt
+++ b/Documentation/gittutorial.txt
@@ -207,7 +207,7 @@ automatically.  The asterisk marks the branch you are currently on;
 type
 
 ------------------------------------------------
-$ git checkout experimental
+$ git switch experimental
 ------------------------------------------------
 
 to switch to the experimental branch.  Now edit a file, commit the
@@ -216,7 +216,7 @@ change, and switch back to the master branch:
 ------------------------------------------------
 (edit file)
 $ git commit -a
-$ git checkout master
+$ git switch master
 ------------------------------------------------
 
 Check that the change you made is no longer visible, since it was
diff --git a/Documentation/revisions.txt b/Documentation/revisions.txt
index 72daa20e76..a1c7a65da6 100644
--- a/Documentation/revisions.txt
+++ b/Documentation/revisions.txt
@@ -115,7 +115,7 @@ Here's an example to make it more clear:
 ------------------------------
 $ git config push.default current
 $ git config remote.pushdefault myfork
-$ git checkout -b mybranch origin/master
+$ git switch -c mybranch origin/master
 
 $ git rev-parse --symbolic-full-name @{upstream}
 refs/remotes/origin/master
diff --git a/Documentation/user-manual.txt b/Documentation/user-manual.txt
index eff7890274..766e64d0e1 100644
--- a/Documentation/user-manual.txt
+++ b/Documentation/user-manual.txt
@@ -122,10 +122,10 @@ Tags are expected to always point at the same version of a project,
 while heads are expected to advance as development progresses.
 
 Create a new branch head pointing to one of these versions and check it
-out using linkgit:git-checkout[1]:
+out using linkgit:git-switch[1]:
 
 ------------------------------------------------
-$ git checkout -b new v2.6.13
+$ git switch -c new v2.6.13
 ------------------------------------------------
 
 The working directory then reflects the contents that the project had
@@ -282,10 +282,10 @@ a summary of the commands:
 	this command will fail with a warning.
 `git branch -D <branch>`::
 	delete the branch `<branch>` irrespective of its merged status.
-`git checkout <branch>`::
+`git switch <branch>`::
 	make the current branch `<branch>`, updating the working
 	directory to reflect the version referenced by `<branch>`.
-`git checkout -b <new> <start-point>`::
+`git switch -c <new> <start-point>`::
 	create a new branch `<new>` referencing `<start-point>`, and
 	check it out.
 
@@ -302,22 +302,22 @@ ref: refs/heads/master
 Examining an old version without creating a new branch
 ------------------------------------------------------
 
-The `git checkout` command normally expects a branch head, but will also
+The `git switch` command normally expects a branch head, but will also
 accept an arbitrary commit; for example, you can check out the commit
 referenced by a tag:
 
 ------------------------------------------------
-$ git checkout v2.6.17
+$ git switch --detach v2.6.17
 Note: checking out 'v2.6.17'.
 
 You are in 'detached HEAD' state. You can look around, make experimental
 changes and commit them, and you can discard any commits you make in this
-state without impacting any branches by performing another checkout.
+state without impacting any branches by performing another switch.
 
 If you want to create a new branch to retain commits you create, you may
-do so (now or later) by using -b with the checkout command again. Example:
+do so (now or later) by using -c with the switch command again. Example:
 
-  git checkout -b new_branch_name
+  git switch -c new_branch_name
 
 HEAD is now at 427abfa Linux v2.6.17
 ------------------------------------------------
@@ -373,7 +373,7 @@ You might want to build on one of these remote-tracking branches
 on a branch of your own, just as you would for a tag:
 
 ------------------------------------------------
-$ git checkout -b my-todo-copy origin/todo
+$ git switch -c my-todo-copy origin/todo
 ------------------------------------------------
 
 You can also check out `origin/todo` directly to examine it or
@@ -2211,8 +2211,8 @@ $ git branch --track release origin/master
 These can be easily kept up to date using linkgit:git-pull[1].
 
 -------------------------------------------------
-$ git checkout test && git pull
-$ git checkout release && git pull
+$ git switch test && git pull
+$ git switch release && git pull
 -------------------------------------------------
 
 Important note!  If you have any local changes in these branches, then
@@ -2264,7 +2264,7 @@ tested changes
 2) help future bug hunters that use `git bisect` to find problems
 
 -------------------------------------------------
-$ git checkout -b speed-up-spinlocks v2.6.35
+$ git switch -c speed-up-spinlocks v2.6.35
 -------------------------------------------------
 
 Now you apply the patch(es), run some tests, and commit the change(s).  If
@@ -2279,7 +2279,7 @@ When you are happy with the state of this change, you can merge it into the
 "test" branch in preparation to make it public:
 
 -------------------------------------------------
-$ git checkout test && git merge speed-up-spinlocks
+$ git switch test && git merge speed-up-spinlocks
 -------------------------------------------------
 
 It is unlikely that you would have any conflicts here ... but you might if you
@@ -2291,7 +2291,7 @@ see the value of keeping each patch (or patch series) in its own branch.  It
 means that the patches can be moved into the `release` tree in any order.
 
 -------------------------------------------------
-$ git checkout release && git merge speed-up-spinlocks
+$ git switch release && git merge speed-up-spinlocks
 -------------------------------------------------
 
 After a while, you will have a number of branches, and despite the
@@ -2512,7 +2512,7 @@ Suppose that you create a branch `mywork` on a remote-tracking branch
 `origin`, and create some commits on top of it:
 
 -------------------------------------------------
-$ git checkout -b mywork origin
+$ git switch -c mywork origin
 $ vi file.txt
 $ git commit
 $ vi otherfile.txt
@@ -2552,7 +2552,7 @@ commits without any merges, you may instead choose to use
 linkgit:git-rebase[1]:
 
 -------------------------------------------------
-$ git checkout mywork
+$ git switch mywork
 $ git rebase origin
 -------------------------------------------------
 
@@ -3668,13 +3668,13 @@ change within the submodule, and then update the superproject to reference the
 new commit:
 
 -------------------------------------------------
-$ git checkout master
+$ git switch master
 -------------------------------------------------
 
 or
 
 -------------------------------------------------
-$ git checkout -b fix-up
+$ git switch -c fix-up
 -------------------------------------------------
 
 then
@@ -4194,7 +4194,7 @@ start.
 A good place to start is with the contents of the initial commit, with:
 
 ----------------------------------------------------
-$ git checkout e83c5163
+$ git switch --detach e83c5163
 ----------------------------------------------------
 
 The initial revision lays the foundation for almost everything Git has
@@ -4437,10 +4437,10 @@ Managing branches
 -----------------
 
 -----------------------------------------------
-$ git branch	     # list all local branches in this repo
-$ git checkout test  # switch working directory to branch "test"
-$ git branch new     # create branch "new" starting at current HEAD
-$ git branch -d new  # delete branch "new"
+$ git branch			# list all local branches in this repo
+$ git switch test	        # switch working directory to branch "test"
+$ git branch new		# create branch "new" starting at current HEAD
+$ git branch -d new		# delete branch "new"
 -----------------------------------------------
 
 Instead of basing a new branch on current HEAD (the default), use:
@@ -4456,7 +4456,7 @@ $ git branch new test~10 # ten commits before tip of branch "test"
 Create and switch to a new branch at the same time:
 
 -----------------------------------------------
-$ git checkout -b new v2.6.15
+$ git switch -c new v2.6.15
 -----------------------------------------------
 
 Update and examine branches from the repository you cloned from:
@@ -4467,7 +4467,7 @@ $ git branch -r		# list
   origin/master
   origin/next
   ...
-$ git checkout -b masterwork origin/master
+$ git switch -c masterwork origin/master
 -----------------------------------------------
 
 Fetch a branch from a different repository, and give it a new
diff --git a/advice.c b/advice.c
index 567209aa79..835219b51b 100644
--- a/advice.c
+++ b/advice.c
@@ -191,13 +191,16 @@ void NORETURN die_conclude_merge(void)
 void detach_advice(const char *new_name)
 {
 	const char *fmt =
-	_("Note: checking out '%s'.\n\n"
+	_("Note: checking out '%s'.\n"
+	"\n"
 	"You are in 'detached HEAD' state. You can look around, make experimental\n"
 	"changes and commit them, and you can discard any commits you make in this\n"
-	"state without impacting any branches by performing another checkout.\n\n"
+	"state without impacting any branches by performing another checkout.\n"
+	"\n"
 	"If you want to create a new branch to retain commits you create, you may\n"
-	"do so (now or later) by using -b with the checkout command again. Example:\n\n"
-	"  git checkout -b <new-branch-name>\n\n");
+	"do so (now or later) by using -b with the checkout command again. Example:\n"
+	"\n"
+	"  git switch -c <new-branch-name>\n\n");
 
 	fprintf(stderr, fmt, new_name);
 }
diff --git a/builtin/clone.c b/builtin/clone.c
index 7c7f98c72c..b06f0ed735 100644
--- a/builtin/clone.c
+++ b/builtin/clone.c
@@ -491,7 +491,7 @@ static enum {
 static const char junk_leave_repo_msg[] =
 N_("Clone succeeded, but checkout failed.\n"
    "You can inspect what was checked out with 'git status'\n"
-   "and retry the checkout with 'git checkout -f HEAD'\n");
+   "and retry the checkout with 'git switch -f HEAD'\n");
 
 static void remove_junk(void)
 {
diff --git a/sha1-name.c b/sha1-name.c
index a656481c6a..e5f0832995 100644
--- a/sha1-name.c
+++ b/sha1-name.c
@@ -745,7 +745,7 @@ static int get_oid_basic(const char *str, int len, struct object_id *oid,
 	"because it will be ignored when you just specify 40-hex. These refs\n"
 	"may be created by mistake. For example,\n"
 	"\n"
-	"  git checkout -b $br $(git rev-parse ...)\n"
+	"  git switch -c $br $(git rev-parse ...)\n"
 	"\n"
 	"where \"$br\" is somehow empty and a 40-hex ref is created. Please\n"
 	"examine these refs and maybe delete them. Turn this message off by\n"
diff --git a/t/t2020-checkout-detach.sh b/t/t2020-checkout-detach.sh
index 1fa670625c..50f7d6c15c 100755
--- a/t/t2020-checkout-detach.sh
+++ b/t/t2020-checkout-detach.sh
@@ -204,7 +204,7 @@ test_expect_success 'describe_detached_head prints no SHA-1 ellipsis when not as
 	If you want to create a new branch to retain commits you create, you may
 	do so (now or later) by using -b with the checkout command again. Example:
 
-	  git checkout -b <new-branch-name>
+	  git switch -c <new-branch-name>
 
 	HEAD is now at \$commit three
 	EOF
@@ -280,7 +280,7 @@ test_expect_success 'describe_detached_head does print SHA-1 ellipsis when asked
 	If you want to create a new branch to retain commits you create, you may
 	do so (now or later) by using -b with the checkout command again. Example:
 
-	  git checkout -b <new-branch-name>
+	  git switch -c <new-branch-name>
 
 	HEAD is now at \$commit... three
 	EOF

diff --git a/Documentation/git-checkout.txt b/Documentation/git-checkout.txt
index ce7d38b8b7..bc7fbdb8d2 100644
--- a/Documentation/git-checkout.txt
+++ b/Documentation/git-checkout.txt
@@ -23,7 +23,7 @@ or the specified tree.  If no paths are given, 'git checkout' will
 also update `HEAD` to set the specified branch as the current
 branch.
 
-'git checkout' <branch>::
+'git checkout' [<branch>]::
 	To prepare for working on <branch>, switch to it by updating
 	the index and the files in the working tree, and by pointing
 	HEAD at the branch. Local modifications to the files in the

Documentation/git-checkout.txt, Documentation/git-merge.txt

diff --git a/Documentation/git-checkout.txt b/Documentation/git-checkout.txt
index bc7fbdb8d2..9ac01f7967 100644
--- a/Documentation/git-checkout.txt
+++ b/Documentation/git-checkout.txt
@@ -270,6 +270,11 @@ Note that this option uses the no overlay mode by default (see also
 	out anyway. In other words, the ref can be held by more than one
 	worktree.
 
+--[no-]overwrite-ignore::
+	Silently overwrite ignored files when switching branches. This
+	is the default behavior. Use --no-overwrite-ignore to abort
+	the operation when the new branch contains ignored files.
+
 --[no-]recurse-submodules::
 	Using --recurse-submodules will update the content of all initialized
 	submodules according to the commit recorded in the superproject. If
diff --git a/Documentation/git-merge.txt b/Documentation/git-merge.txt
index 4cc86469f3..0480e9d0f0 100644
--- a/Documentation/git-merge.txt
+++ b/Documentation/git-merge.txt
@@ -87,6 +87,10 @@ will be appended to the specified message.
 	Allow the rerere mechanism to update the index with the
 	result of auto-conflict resolution if possible.
 
+--[no-]overwrite-ignore::
+	Silently overwrite ignored files from the merge result. This
+	is the default behavior. Use --no-overwrite-ignore to abort.
+
 --abort::
 	Abort the current conflict resolution process, and
 	try to reconstruct the pre-merge state.

diff --git a/t/t2014-switch.sh b/t/t2014-checkout-switch.sh
similarity index 100%
rename from t/t2014-switch.sh
rename to t/t2014-checkout-switch.sh

diff --git a/builtin/checkout.c b/builtin/checkout.c
index f63d864a91..12b7e08d4e 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -1068,6 +1068,34 @@ static int git_checkout_config(const char *var, const char *value, void *cb)
 	return git_xmerge_config(var, value, NULL);
 }
 
+static void setup_new_branch_info_and_source_tree(
+	struct branch_info *new_branch_info,
+	struct checkout_opts *opts,
+	struct object_id *rev,
+	const char *arg)
+{
+	struct tree **source_tree = &opts->source_tree;
+	struct object_id branch_rev;
+
+	new_branch_info->name = arg;
+	setup_branch_path(new_branch_info);
+
+	if (!check_refname_format(new_branch_info->path, 0) &&
+	    !read_ref(new_branch_info->path, &branch_rev))
+		oidcpy(rev, &branch_rev);
+	else
+		new_branch_info->path = NULL; /* not an existing branch */
+
+	new_branch_info->commit = lookup_commit_reference_gently(the_repository, rev, 1);
+	if (!new_branch_info->commit) {
+		/* not a commit */
+		*source_tree = parse_tree_indirect(rev);
+	} else {
+		parse_commit_or_die(new_branch_info->commit);
+		*source_tree = get_commit_tree(new_branch_info->commit);
+	}
+}
+
 static int parse_branchname_arg(int argc, const char **argv,
 				int dwim_new_local_branch_ok,
 				struct branch_info *new_branch_info,
@@ -1075,10 +1103,8 @@ static int parse_branchname_arg(int argc, const char **argv,
 				struct object_id *rev,
 				int *dwim_remotes_matched)
 {
-	struct tree **source_tree = &opts->source_tree;
 	const char **new_branch = &opts->new_branch;
 	int argcount = 0;
-	struct object_id branch_rev;
 	const char *arg;
 	int dash_dash_pos;
 	int has_dash_dash = 0;
@@ -1200,26 +1226,11 @@ static int parse_branchname_arg(int argc, const char **argv,
 	argv++;
 	argc--;
 
-	new_branch_info->name = arg;
-	setup_branch_path(new_branch_info);
-
-	if (!check_refname_format(new_branch_info->path, 0) &&
-	    !read_ref(new_branch_info->path, &branch_rev))
-		oidcpy(rev, &branch_rev);
-	else
-		new_branch_info->path = NULL; /* not an existing branch */
+	setup_new_branch_info_and_source_tree(new_branch_info, opts, rev, arg);
 
-	new_branch_info->commit = lookup_commit_reference_gently(the_repository, rev, 1);
-	if (!new_branch_info->commit) {
-		/* not a commit */
-		*source_tree = parse_tree_indirect(rev);
-	} else {
-		parse_commit_or_die(new_branch_info->commit);
-		*source_tree = get_commit_tree(new_branch_info->commit);
-	}
-
-	if (!*source_tree)                   /* case (1): want a tree */
+	if (!opts->source_tree)                   /* case (1): want a tree */
 		die(_("reference is not a tree: %s"), arg);
+
 	if (!has_dash_dash) {	/* case (3).(d) -> (1) */
 		/*
 		 * Do not complain the most common case

diff --git a/builtin/checkout.c b/builtin/checkout.c
index 12b7e08d4e..66f99e788d 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -1326,82 +1326,83 @@ static int checkout_branch(struct checkout_opts *opts,
 
 int cmd_checkout(int argc, const char **argv, const char *prefix)
 {
-	struct checkout_opts opts;
+	struct checkout_opts real_opts;
+	struct checkout_opts *opts = &real_opts;
 	struct branch_info new_branch_info;
 	char *conflict_style = NULL;
 	int dwim_new_local_branch, no_dwim_new_local_branch = 0;
 	int dwim_remotes_matched = 0;
 	struct option options[] = {
-		OPT__QUIET(&opts.quiet, N_("suppress progress reporting")),
-		OPT_STRING('b', NULL, &opts.new_branch, N_("branch"),
+		OPT__QUIET(&opts->quiet, N_("suppress progress reporting")),
+		OPT_STRING('b', NULL, &opts->new_branch, N_("branch"),
 			   N_("create and checkout a new branch")),
-		OPT_STRING('B', NULL, &opts.new_branch_force, N_("branch"),
+		OPT_STRING('B', NULL, &opts->new_branch_force, N_("branch"),
 			   N_("create/reset and checkout a branch")),
-		OPT_BOOL('l', NULL, &opts.new_branch_log, N_("create reflog for new branch")),
-		OPT_BOOL(0, "detach", &opts.force_detach, N_("detach HEAD at named commit")),
-		OPT_SET_INT('t', "track",  &opts.track, N_("set upstream info for new branch"),
+		OPT_BOOL('l', NULL, &opts->new_branch_log, N_("create reflog for new branch")),
+		OPT_BOOL(0, "detach", &opts->force_detach, N_("detach HEAD at named commit")),
+		OPT_SET_INT('t', "track",  &opts->track, N_("set upstream info for new branch"),
 			BRANCH_TRACK_EXPLICIT),
-		OPT_STRING(0, "orphan", &opts.new_orphan_branch, N_("new-branch"), N_("new unparented branch")),
-		OPT_SET_INT_F('2', "ours", &opts.writeout_stage,
+		OPT_STRING(0, "orphan", &opts->new_orphan_branch, N_("new-branch"), N_("new unparented branch")),
+		OPT_SET_INT_F('2', "ours", &opts->writeout_stage,
 			      N_("checkout our version for unmerged files"),
 			      2, PARSE_OPT_NONEG),
-		OPT_SET_INT_F('3', "theirs", &opts.writeout_stage,
+		OPT_SET_INT_F('3', "theirs", &opts->writeout_stage,
 			      N_("checkout their version for unmerged files"),
 			      3, PARSE_OPT_NONEG),
-		OPT__FORCE(&opts.force, N_("force checkout (throw away local modifications)"),
+		OPT__FORCE(&opts->force, N_("force checkout (throw away local modifications)"),
 			   PARSE_OPT_NOCOMPLETE),
-		OPT_BOOL('m', "merge", &opts.merge, N_("perform a 3-way merge with the new branch")),
-		OPT_BOOL_F(0, "overwrite-ignore", &opts.overwrite_ignore,
+		OPT_BOOL('m', "merge", &opts->merge, N_("perform a 3-way merge with the new branch")),
+		OPT_BOOL_F(0, "overwrite-ignore", &opts->overwrite_ignore,
 			   N_("update ignored files (default)"),
 			   PARSE_OPT_NOCOMPLETE),
 		OPT_STRING(0, "conflict", &conflict_style, N_("style"),
 			   N_("conflict style (merge or diff3)")),
-		OPT_BOOL('p', "patch", &opts.patch_mode, N_("select hunks interactively")),
-		OPT_BOOL(0, "ignore-skip-worktree-bits", &opts.ignore_skipworktree,
+		OPT_BOOL('p', "patch", &opts->patch_mode, N_("select hunks interactively")),
+		OPT_BOOL(0, "ignore-skip-worktree-bits", &opts->ignore_skipworktree,
 			 N_("do not limit pathspecs to sparse entries only")),
 		OPT_BOOL(0, "no-guess", &no_dwim_new_local_branch,
 			 N_("do not second guess 'git checkout <no-such-branch>'")),
-		OPT_BOOL(0, "ignore-other-worktrees", &opts.ignore_other_worktrees,
+		OPT_BOOL(0, "ignore-other-worktrees", &opts->ignore_other_worktrees,
 			 N_("do not check if another worktree is holding the given ref")),
 		{ OPTION_CALLBACK, 0, "recurse-submodules", NULL,
 			    "checkout", "control recursive updating of submodules",
 			    PARSE_OPT_OPTARG, option_parse_recurse_submodules_worktree_updater },
-		OPT_BOOL(0, "progress", &opts.show_progress, N_("force progress reporting")),
-		OPT_BOOL(0, "overlay", &opts.overlay_mode, N_("use overlay mode (default)")),
+		OPT_BOOL(0, "progress", &opts->show_progress, N_("force progress reporting")),
+		OPT_BOOL(0, "overlay", &opts->overlay_mode, N_("use overlay mode (default)")),
 		OPT_END(),
 	};
 
-	memset(&opts, 0, sizeof(opts));
+	memset(opts, 0, sizeof(*opts));
 	memset(&new_branch_info, 0, sizeof(new_branch_info));
-	opts.overwrite_ignore = 1;
-	opts.prefix = prefix;
-	opts.show_progress = -1;
-	opts.overlay_mode = -1;
+	opts->overwrite_ignore = 1;
+	opts->prefix = prefix;
+	opts->show_progress = -1;
+	opts->overlay_mode = -1;
 
-	git_config(git_checkout_config, &opts);
+	git_config(git_checkout_config, opts);
 
-	opts.track = BRANCH_TRACK_UNSPECIFIED;
+	opts->track = BRANCH_TRACK_UNSPECIFIED;
 
 	argc = parse_options(argc, argv, prefix, options, checkout_usage,
 			     PARSE_OPT_KEEP_DASHDASH);
 
 	dwim_new_local_branch = !no_dwim_new_local_branch;
-	if (opts.show_progress < 0) {
-		if (opts.quiet)
-			opts.show_progress = 0;
+	if (opts->show_progress < 0) {
+		if (opts->quiet)
+			opts->show_progress = 0;
 		else
-			opts.show_progress = isatty(2);
+			opts->show_progress = isatty(2);
 	}
 
 	if (conflict_style) {
-		opts.merge = 1; /* implied */
+		opts->merge = 1; /* implied */
 		git_xmerge_config("merge.conflictstyle", conflict_style, NULL);
 	}
 
-	if ((!!opts.new_branch + !!opts.new_branch_force + !!opts.new_orphan_branch) > 1)
+	if ((!!opts->new_branch + !!opts->new_branch_force + !!opts->new_orphan_branch) > 1)
 		die(_("-b, -B and --orphan are mutually exclusive"));
 
-	if (opts.overlay_mode == 1 && opts.patch_mode)
+	if (opts->overlay_mode == 1 && opts->patch_mode)
 		die(_("-p and --overlay are mutually exclusive"));
 
 	/*
@@ -1409,14 +1410,14 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 	 * and new_branch_force and new_orphan_branch will tell us which one of
 	 * -b/-B/--orphan is being used.
 	 */
-	if (opts.new_branch_force)
-		opts.new_branch = opts.new_branch_force;
+	if (opts->new_branch_force)
+		opts->new_branch = opts->new_branch_force;
 
-	if (opts.new_orphan_branch)
-		opts.new_branch = opts.new_orphan_branch;
+	if (opts->new_orphan_branch)
+		opts->new_branch = opts->new_orphan_branch;
 
 	/* --track without -b/-B/--orphan should DWIM */
-	if (opts.track != BRANCH_TRACK_UNSPECIFIED && !opts.new_branch) {
+	if (opts->track != BRANCH_TRACK_UNSPECIFIED && !opts->new_branch) {
 		const char *argv0 = argv[0];
 		if (!argc || !strcmp(argv0, "--"))
 			die(_("--track needs a branch name"));
@@ -1425,7 +1426,7 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 		argv0 = strchr(argv0, '/');
 		if (!argv0 || !argv0[1])
 			die(_("missing branch name; try -b"));
-		opts.new_branch = argv0 + 1;
+		opts->new_branch = argv0 + 1;
 	}
 
 	/*
@@ -1444,56 +1445,56 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 	if (argc) {
 		struct object_id rev;
 		int dwim_ok =
-			!opts.patch_mode &&
+			!opts->patch_mode &&
 			dwim_new_local_branch &&
-			opts.track == BRANCH_TRACK_UNSPECIFIED &&
-			!opts.new_branch;
+			opts->track == BRANCH_TRACK_UNSPECIFIED &&
+			!opts->new_branch;
 		int n = parse_branchname_arg(argc, argv, dwim_ok,
-					     &new_branch_info, &opts, &rev,
+					     &new_branch_info, opts, &rev,
 					     &dwim_remotes_matched);
 		argv += n;
 		argc -= n;
 	}
 
 	if (argc) {
-		parse_pathspec(&opts.pathspec, 0,
-			       opts.patch_mode ? PATHSPEC_PREFIX_ORIGIN : 0,
+		parse_pathspec(&opts->pathspec, 0,
+			       opts->patch_mode ? PATHSPEC_PREFIX_ORIGIN : 0,
 			       prefix, argv);
 
-		if (!opts.pathspec.nr)
+		if (!opts->pathspec.nr)
 			die(_("invalid path specification"));
 
 		/*
 		 * Try to give more helpful suggestion.
 		 * new_branch && argc > 1 will be caught later.
 		 */
-		if (opts.new_branch && argc == 1)
+		if (opts->new_branch && argc == 1)
 			die(_("'%s' is not a commit and a branch '%s' cannot be created from it"),
-				argv[0], opts.new_branch);
+				argv[0], opts->new_branch);
 
-		if (opts.force_detach)
+		if (opts->force_detach)
 			die(_("git checkout: --detach does not take a path argument '%s'"),
 			    argv[0]);
 
-		if (1 < !!opts.writeout_stage + !!opts.force + !!opts.merge)
+		if (1 < !!opts->writeout_stage + !!opts->force + !!opts->merge)
 			die(_("git checkout: --ours/--theirs, --force and --merge are incompatible when\n"
 			      "checking out of the index."));
 	}
 
-	if (opts.new_branch) {
+	if (opts->new_branch) {
 		struct strbuf buf = STRBUF_INIT;
 
-		if (opts.new_branch_force)
-			opts.branch_exists = validate_branchname(opts.new_branch, &buf);
+		if (opts->new_branch_force)
+			opts->branch_exists = validate_branchname(opts->new_branch, &buf);
 		else
-			opts.branch_exists =
-				validate_new_branchname(opts.new_branch, &buf, 0);
+			opts->branch_exists =
+				validate_new_branchname(opts->new_branch, &buf, 0);
 		strbuf_release(&buf);
 	}
 
 	UNLEAK(opts);
-	if (opts.patch_mode || opts.pathspec.nr) {
-		int ret = checkout_paths(&opts, new_branch_info.name);
+	if (opts->patch_mode || opts->pathspec.nr) {
+		int ret = checkout_paths(opts, new_branch_info.name);
 		if (ret && dwim_remotes_matched > 1 &&
 		    advice_checkout_ambiguous_remote_branch_name)
 			advise(_("'%s' matched more than one remote tracking branch.\n"
@@ -1512,6 +1513,6 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 			       dwim_remotes_matched);
 		return ret;
 	} else {
-		return checkout_branch(&opts, &new_branch_info);
+		return checkout_branch(opts, &new_branch_info);
 	}
 }

diff --git a/builtin/checkout.c b/builtin/checkout.c
index 66f99e788d..5914dd3619 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -46,6 +46,8 @@ struct checkout_opts {
 	int show_progress;
 	int count_checkout_paths;
 	int overlay_mode;
+	int no_dwim_new_local_branch;
+
 	/*
 	 * If new checkout options are added, skip_merge_working_tree
 	 * should be updated accordingly.
@@ -57,6 +59,7 @@ struct checkout_opts {
 	int new_branch_log;
 	enum branch_track track;
 	struct diff_options diff_options;
+	char *conflict_style;
 
 	int branch_exists;
 	const char *prefix;
@@ -1329,8 +1332,7 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 	struct checkout_opts real_opts;
 	struct checkout_opts *opts = &real_opts;
 	struct branch_info new_branch_info;
-	char *conflict_style = NULL;
-	int dwim_new_local_branch, no_dwim_new_local_branch = 0;
+	int dwim_new_local_branch;
 	int dwim_remotes_matched = 0;
 	struct option options[] = {
 		OPT__QUIET(&opts->quiet, N_("suppress progress reporting")),
@@ -1355,12 +1357,12 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 		OPT_BOOL_F(0, "overwrite-ignore", &opts->overwrite_ignore,
 			   N_("update ignored files (default)"),
 			   PARSE_OPT_NOCOMPLETE),
-		OPT_STRING(0, "conflict", &conflict_style, N_("style"),
+		OPT_STRING(0, "conflict", &opts->conflict_style, N_("style"),
 			   N_("conflict style (merge or diff3)")),
 		OPT_BOOL('p', "patch", &opts->patch_mode, N_("select hunks interactively")),
 		OPT_BOOL(0, "ignore-skip-worktree-bits", &opts->ignore_skipworktree,
 			 N_("do not limit pathspecs to sparse entries only")),
-		OPT_BOOL(0, "no-guess", &no_dwim_new_local_branch,
+		OPT_BOOL(0, "no-guess", &opts->no_dwim_new_local_branch,
 			 N_("do not second guess 'git checkout <no-such-branch>'")),
 		OPT_BOOL(0, "ignore-other-worktrees", &opts->ignore_other_worktrees,
 			 N_("do not check if another worktree is holding the given ref")),
@@ -1378,6 +1380,7 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 	opts->prefix = prefix;
 	opts->show_progress = -1;
 	opts->overlay_mode = -1;
+	opts->no_dwim_new_local_branch = 0;
 
 	git_config(git_checkout_config, opts);
 
@@ -1386,7 +1389,7 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 	argc = parse_options(argc, argv, prefix, options, checkout_usage,
 			     PARSE_OPT_KEEP_DASHDASH);
 
-	dwim_new_local_branch = !no_dwim_new_local_branch;
+	dwim_new_local_branch = !opts->no_dwim_new_local_branch;
 	if (opts->show_progress < 0) {
 		if (opts->quiet)
 			opts->show_progress = 0;
@@ -1394,9 +1397,9 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 			opts->show_progress = isatty(2);
 	}
 
-	if (conflict_style) {
+	if (opts->conflict_style) {
 		opts->merge = 1; /* implied */
-		git_xmerge_config("merge.conflictstyle", conflict_style, NULL);
+		git_xmerge_config("merge.conflictstyle", opts->conflict_style, NULL);
 	}
 
 	if ((!!opts->new_branch + !!opts->new_branch_force + !!opts->new_orphan_branch) > 1)

builtin/checkout.c, parse-options-cb.c, parse-options.h

diff --git a/builtin/checkout.c b/builtin/checkout.c
index 5914dd3619..8ea1349cce 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -1327,15 +1327,31 @@ static int checkout_branch(struct checkout_opts *opts,
 	return switch_branches(opts, new_branch_info);
 }
 
-int cmd_checkout(int argc, const char **argv, const char *prefix)
+static struct option *add_common_options(struct checkout_opts *opts,
+					 struct option *prevopts)
 {
-	struct checkout_opts real_opts;
-	struct checkout_opts *opts = &real_opts;
-	struct branch_info new_branch_info;
-	int dwim_new_local_branch;
-	int dwim_remotes_matched = 0;
 	struct option options[] = {
 		OPT__QUIET(&opts->quiet, N_("suppress progress reporting")),
+		{ OPTION_CALLBACK, 0, "recurse-submodules", NULL,
+			    "checkout", "control recursive updating of submodules",
+			    PARSE_OPT_OPTARG, option_parse_recurse_submodules_worktree_updater },
+		OPT_BOOL(0, "progress", &opts->show_progress, N_("force progress reporting")),
+		OPT__FORCE(&opts->force, N_("force checkout (throw away local modifications)"),
+			   PARSE_OPT_NOCOMPLETE),
+		OPT_BOOL('m', "merge", &opts->merge, N_("perform a 3-way merge with the new branch")),
+		OPT_STRING(0, "conflict", &opts->conflict_style, N_("style"),
+			   N_("conflict style (merge or diff3)")),
+		OPT_END()
+	};
+	struct option *newopts = parse_options_concat(prevopts, options);
+	free(prevopts);
+	return newopts;
+}
+
+static struct option *add_switch_branch_options(struct checkout_opts *opts,
+						struct option *prevopts)
+{
+	struct option options[] = {
 		OPT_STRING('b', NULL, &opts->new_branch, N_("branch"),
 			   N_("create and checkout a new branch")),
 		OPT_STRING('B', NULL, &opts->new_branch_force, N_("branch"),
@@ -1345,34 +1361,49 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 		OPT_SET_INT('t', "track",  &opts->track, N_("set upstream info for new branch"),
 			BRANCH_TRACK_EXPLICIT),
 		OPT_STRING(0, "orphan", &opts->new_orphan_branch, N_("new-branch"), N_("new unparented branch")),
+		OPT_BOOL_F(0, "overwrite-ignore", &opts->overwrite_ignore,
+			   N_("update ignored files (default)"),
+			   PARSE_OPT_NOCOMPLETE),
+		OPT_BOOL(0, "no-guess", &opts->no_dwim_new_local_branch,
+			 N_("second guess 'git checkout <no-such-branch>'")),
+		OPT_BOOL(0, "ignore-other-worktrees", &opts->ignore_other_worktrees,
+			 N_("do not check if another worktree is holding the given ref")),
+		OPT_END()
+	};
+	struct option *newopts = parse_options_concat(prevopts, options);
+	free(prevopts);
+	return newopts;
+}
+
+static struct option *add_checkout_path_options(struct checkout_opts *opts,
+						struct option *prevopts)
+{
+	struct option options[] = {
 		OPT_SET_INT_F('2', "ours", &opts->writeout_stage,
 			      N_("checkout our version for unmerged files"),
 			      2, PARSE_OPT_NONEG),
 		OPT_SET_INT_F('3', "theirs", &opts->writeout_stage,
 			      N_("checkout their version for unmerged files"),
 			      3, PARSE_OPT_NONEG),
-		OPT__FORCE(&opts->force, N_("force checkout (throw away local modifications)"),
-			   PARSE_OPT_NOCOMPLETE),
-		OPT_BOOL('m', "merge", &opts->merge, N_("perform a 3-way merge with the new branch")),
-		OPT_BOOL_F(0, "overwrite-ignore", &opts->overwrite_ignore,
-			   N_("update ignored files (default)"),
-			   PARSE_OPT_NOCOMPLETE),
-		OPT_STRING(0, "conflict", &opts->conflict_style, N_("style"),
-			   N_("conflict style (merge or diff3)")),
 		OPT_BOOL('p', "patch", &opts->patch_mode, N_("select hunks interactively")),
 		OPT_BOOL(0, "ignore-skip-worktree-bits", &opts->ignore_skipworktree,
 			 N_("do not limit pathspecs to sparse entries only")),
-		OPT_BOOL(0, "no-guess", &opts->no_dwim_new_local_branch,
-			 N_("do not second guess 'git checkout <no-such-branch>'")),
-		OPT_BOOL(0, "ignore-other-worktrees", &opts->ignore_other_worktrees,
-			 N_("do not check if another worktree is holding the given ref")),
-		{ OPTION_CALLBACK, 0, "recurse-submodules", NULL,
-			    "checkout", "control recursive updating of submodules",
-			    PARSE_OPT_OPTARG, option_parse_recurse_submodules_worktree_updater },
-		OPT_BOOL(0, "progress", &opts->show_progress, N_("force progress reporting")),
 		OPT_BOOL(0, "overlay", &opts->overlay_mode, N_("use overlay mode (default)")),
-		OPT_END(),
+		OPT_END()
 	};
+	struct option *newopts = parse_options_concat(prevopts, options);
+	free(prevopts);
+	return newopts;
+}
+
+int cmd_checkout(int argc, const char **argv, const char *prefix)
+{
+	struct checkout_opts real_opts;
+	struct checkout_opts *opts = &real_opts;
+	struct branch_info new_branch_info;
+	int dwim_remotes_matched = 0;
+	int dwim_new_local_branch;
+	struct option *options = NULL;
 
 	memset(opts, 0, sizeof(*opts));
 	memset(&new_branch_info, 0, sizeof(new_branch_info));
@@ -1386,6 +1417,11 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 
 	opts->track = BRANCH_TRACK_UNSPECIFIED;
 
+	options = parse_options_dup(options);
+	options = add_common_options(opts, options);
+	options = add_switch_branch_options(opts, options);
+	options = add_checkout_path_options(opts, options);
+
 	argc = parse_options(argc, argv, prefix, options, checkout_usage,
 			     PARSE_OPT_KEEP_DASHDASH);
 
diff --git a/parse-options-cb.c b/parse-options-cb.c
index e2f3eaed07..76eb5c211b 100644
--- a/parse-options-cb.c
+++ b/parse-options-cb.c
@@ -122,6 +122,23 @@ int parse_opt_tertiary(const struct option *opt, const char *arg, int unset)
 	return 0;
 }
 
+struct option *parse_options_dup(const struct option *o)
+{
+	struct option *opts;
+	int nr = 0;
+
+	while (o && o->type != OPTION_END) {
+		nr++;
+		o++;
+	}
+
+	ALLOC_ARRAY(opts, nr + 1);
+	memcpy(opts, o - nr, sizeof(*o) * nr);
+	memset(opts + nr, 0, sizeof(*opts));
+	opts[nr].type = OPTION_END;
+	return opts;
+}
+
 struct option *parse_options_concat(struct option *a, struct option *b)
 {
 	struct option *ret;
diff --git a/parse-options.h b/parse-options.h
index 14fe32428e..6846a5b1e0 100644
--- a/parse-options.h
+++ b/parse-options.h
@@ -237,7 +237,8 @@ extern int parse_options_step(struct parse_opt_ctx_t *ctx,
 
 extern int parse_options_end(struct parse_opt_ctx_t *ctx);
 
-extern struct option *parse_options_concat(struct option *a, struct option *b);
+struct option *parse_options_dup(const struct option *a);
+struct option *parse_options_concat(struct option *a, struct option *b);
 
 /*----- some often used options -----*/
 extern int parse_opt_abbrev_cb(const struct option *, const char *, int);

.gitignore, Documentation/config/advice.txt, Documentation/config/branch.txt, Documentation/config/checkout.txt, Documentation/config/diff.txt, Documentation/git-checkout.txt, Documentation/git-switch.txt, Documentation/gitattributes.txt, Documentation/githooks.txt, Makefile, builtin.h, builtin/checkout.c, command-list.txt, git.c

diff --git a/.gitignore b/.gitignore
index 0d77ea5894..8e2b89047f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -167,6 +167,7 @@
 /git-submodule
 /git-submodule--helper
 /git-svn
+/git-switch
 /git-symbolic-ref
 /git-tag
 /git-unpack-file
diff --git a/Documentation/config/advice.txt b/Documentation/config/advice.txt
index 88620429ea..239d479506 100644
--- a/Documentation/config/advice.txt
+++ b/Documentation/config/advice.txt
@@ -42,7 +42,8 @@ advice.*::
 		state in the output of linkgit:git-status[1], in
 		the template shown when writing commit messages in
 		linkgit:git-commit[1], and in the help message shown
-		by linkgit:git-checkout[1] when switching branch.
+		by linkgit:git-switch[1] or
+		linkgit:git-checkout[1] when switching branch.
 	statusUoption::
 		Advise to consider using the `-u` option to linkgit:git-status[1]
 		when the command takes more than 2 seconds to enumerate untracked
@@ -62,12 +63,14 @@ advice.*::
 		your information is guessed from the system username and
 		domain name.
 	detachedHead::
-		Advice shown when you used linkgit:git-checkout[1] to
-		move to the detach HEAD state, to instruct how to create
-		a local branch after the fact.
+		Advice shown when you used
+		linkgit:git-switch[1] or linkgit:git-checkout[1]
+		to move to the detach HEAD state, to instruct how to
+		create a local branch after the fact.
 	checkoutAmbiguousRemoteBranchName::
 		Advice shown when the argument to
-		linkgit:git-checkout[1] ambiguously resolves to a
+		linkgit:git-checkout[1] and linkgit:git-switch[1]
+		ambiguously resolves to a
 		remote tracking branch on more than one remote in
 		situations where an unambiguous argument would have
 		otherwise caused a remote-tracking branch to be
diff --git a/Documentation/config/branch.txt b/Documentation/config/branch.txt
index 019d60ede2..8050466159 100644
--- a/Documentation/config/branch.txt
+++ b/Documentation/config/branch.txt
@@ -1,5 +1,5 @@
 branch.autoSetupMerge::
-	Tells 'git branch' and 'git checkout' to set up new branches
+	Tells 'git branch', 'git switch' and 'git checkout' to set up new branches
 	so that linkgit:git-pull[1] will appropriately merge from the
 	starting point branch. Note that even if this option is not set,
 	this behavior can be chosen per-branch using the `--track`
@@ -11,7 +11,7 @@ branch.autoSetupMerge::
 	branch. This option defaults to true.
 
 branch.autoSetupRebase::
-	When a new branch is created with 'git branch' or 'git checkout'
+	When a new branch is created with 'git branch', 'git switch' or 'git checkout'
 	that tracks another branch, this variable tells Git to set
 	up pull to rebase instead of merge (see "branch.<name>.rebase").
 	When `never`, rebase is never automatically set to true.
diff --git a/Documentation/config/checkout.txt b/Documentation/config/checkout.txt
index 73380a8d86..fc211eca58 100644
--- a/Documentation/config/checkout.txt
+++ b/Documentation/config/checkout.txt
@@ -1,5 +1,6 @@
 checkout.defaultRemote::
-	When you run 'git checkout <something>' and only have one
+	When you run 'git checkout <something>'
+	or 'git switch <something>' and only have one
 	remote, it may implicitly fall back on checking out and
 	tracking e.g. 'origin/<something>'. This stops working as soon
 	as you have more than one remote with a '<something>'
@@ -8,8 +9,10 @@ checkout.defaultRemote::
 	disambiguation. The typical use-case is to set this to
 	`origin`.
 +
-Currently this is used by linkgit:git-checkout[1] when 'git checkout
-<something>' will checkout the '<something>' branch on another remote,
+Currently this is used by linkgit:git-switch[1] and
+linkgit:git-checkout[1] when 'git checkout <something>'
+or 'git switch <something>'
+will checkout the '<something>' branch on another remote,
 and by linkgit:git-worktree[1] when 'git worktree add' refers to a
 remote branch. This setting might be used for other checkout-like
 commands or functionality in the future.
diff --git a/Documentation/config/diff.txt b/Documentation/config/diff.txt
index e48bb987d7..b3b304ee12 100644
--- a/Documentation/config/diff.txt
+++ b/Documentation/config/diff.txt
@@ -78,7 +78,8 @@ diff.external::
 diff.ignoreSubmodules::
 	Sets the default value of --ignore-submodules. Note that this
 	affects only 'git diff' Porcelain, and not lower level 'diff'
-	commands such as 'git diff-files'. 'git checkout' also honors
+	commands such as 'git diff-files'. 'git checkout'
+	and 'git switch' also honor
 	this setting when reporting uncommitted changes. Setting it to
 	'all' disables the submodule summary normally shown by 'git commit'
 	and 'git status' when `status.submoduleSummary` is set unless it is
diff --git a/Documentation/git-checkout.txt b/Documentation/git-checkout.txt
index 9ac01f7967..31c6cbef19 100644
--- a/Documentation/git-checkout.txt
+++ b/Documentation/git-checkout.txt
@@ -556,6 +556,10 @@ $ edit frotz
 $ git add frotz
 ------------
 
+SEE ALSO
+--------
+linkgit:git-switch[1]
+
 GIT
 ---
 Part of the linkgit:git[1] suite
diff --git a/Documentation/git-switch.txt b/Documentation/git-switch.txt
new file mode 100644
index 0000000000..1a4d156e3c
--- /dev/null
+++ b/Documentation/git-switch.txt
@@ -0,0 +1,257 @@
+git-switch(1)
+=============
+
+NAME
+----
+git-switch - Switch branches
+
+SYNOPSIS
+--------
+[verse]
+'git switch' [<options>] [--guess] <branch>
+'git switch' [<options>] --detach [<start-point>]
+'git switch' [<options>] (-c|-C|--orphan) <new-branch> [<start-point>]
+
+DESCRIPTION
+-----------
+Switch to a specified branch. The working tree and the index are
+updated to match the branch. All new commits will be added to the tip
+of this branch.
+
+Optionally a new branch could be created with either `-c` or `-C`, or
+detach the working tree from any branch with `--detach`, along with
+switching.
+
+Switching branches does not require a clean index and working tree
+(i.e. no differences compared to 'HEAD'). The operation is aborted
+however if the switch leads to loss of local changes, unless told
+otherwise.
+
+OPTIONS
+-------
+<branch>::
+	Branch to switch to.
+
+<new-branch>::
+	Name for the new branch.
+
+<start-point>::
+	The name of a commit at which to switch to before creating a
+	new branch or detach from.
++
+You can use the `"@{-N}"` syntax to refer to the N-th last
+branch/commit switched to "git switch" or "git checkout"
+operation. You may also specify `-` which is synonymous to `"@{-1}`.
++
+As a special case, you may use `"A...B"` as a shortcut for the merge
+base of `A` and `B` if there is exactly one merge base. You can leave
+out at most one of `A` and `B`, in which case it defaults to `HEAD`.
+
+-c <new-branch>::
+--create <new-branch>::
+	Create a new branch named <new-branch> starting at
+	<start-point> before switching to the branch. This is a
+	convenient shortcut for:
++
+------------
+$ git branch <new-branch>
+$ git switch <new-branch>
+------------
+
+-C <new-branch>::
+--force-create <new-branch>::
+	Similar to `--create` except that if <new-branch> already
+	exists, it will be reset to <start-point>. This is a
+	convenient shortcut for:
++
+------------
+$ git branch -f <new-branch>
+$ git switch <new-branch>
+------------
+
+-d::
+--detach::
+	Switch to a commit for inspection and discardable
+	experiments. See the "DETACHED HEAD" section in
+	linkgit:git-checkout[1] for details.
+
+-g::
+--guess::
+	If <branch> is not found but there does exist a tracking
+	branch in exactly one remote (call it <remote>) with a
+	matching name, treat as equivalent to
++
+------------
+$ git switch -c <branch> --track <remote>/<branch>
+------------
++
+If the branch exists in multiple remotes and one of them is named by
+the `checkout.defaultRemote` configuration variable, we'll use that
+one for the purposes of disambiguation, even if the `<branch>` isn't
+unique across all remotes. Set it to e.g. `checkout.defaultRemote=origin`
+to always checkout remote branches from there if `<branch>` is
+ambiguous but exists on the 'origin' remote. See also
+`checkout.defaultRemote` in linkgit:git-config[1].
+
+-q::
+--quiet::
+	Quiet, suppress feedback messages.
+
+-f::
+--force::
+	Proceed even if the index or the working tree differs from
+	HEAD. Both the index and working tree are restored to match
+	the switching target. This is used to throw away local
+	changes.
+
+--[no-]progress::
+	Progress status is reported on the standard error stream
+	by default when it is attached to a terminal, unless `--quiet`
+	is specified. This flag enables progress reporting even if not
+	attached to a terminal, regardless of `--quiet`.
+
+-t::
+--track::
+	When creating a new branch, set up "upstream" configuration.
+	`-c` is implied. See "--track" in linkgit:git-branch[1] for
+	details.
++
+If no `-c` option is given, the name of the new branch will be derived
+from the remote-tracking branch, by looking at the local part of the
+refspec configured for the corresponding remote, and then stripping
+the initial part up to the "*".  This would tell us to use "hack" as
+the local branch when branching off of "origin/hack" (or
+"remotes/origin/hack", or even "refs/remotes/origin/hack").  If the
+given name has no slash, or the above guessing results in an empty
+name, the guessing is aborted.  You can explicitly give a name with
+`-c` in such a case.
+
+--no-track::
+	Do not set up "upstream" configuration, even if the
+	branch.autoSetupMerge configuration variable is true.
+
+-m::
+--merge::
+	If you have local modifications to one or more files that are
+	different between the current branch and the branch to which
+	you are switching, the command refuses to switch branches in
+	order to preserve your modifications in context.  However,
+	with this option, a three-way merge between the current
+	branch, your working tree contents, and the new branch is
+	done, and you will be on the new branch.
++
+When a merge conflict happens, the index entries for conflicting
+paths are left unmerged, and you need to resolve the conflicts
+and mark the resolved paths with `git add` (or `git rm` if the merge
+should result in deletion of the path).
+
+--conflict=<style>::
+	The same as --merge option above, but changes the way the
+	conflicting hunks are presented, overriding the
+	merge.conflictStyle configuration variable.  Possible values are
+	"merge" (default) and "diff3" (in addition to what is shown by
+	"merge" style, shows the original contents).
+
+--orphan <new-branch>::
+	Create a new 'orphan' branch, named <new-branch>, started from
+	<start-point> and switch to it. See explanation of the same
+	option in linkgit:git-checkout[1] for details.
+
+--ignore-other-worktrees::
+	`git switch` refuses when the wanted ref is already
+	checked out by another worktree. This option makes it check
+	the ref out anyway. In other words, the ref can be held by
+	more than one worktree.
+
+--[no-]recurse-submodules::
+	Using --recurse-submodules will update the content of all initialized
+	submodules according to the commit recorded in the superproject. If
+	local modifications in a submodule would be overwritten the checkout
+	will fail unless `-f` is used. If nothing (or --no-recurse-submodules)
+	is used, the work trees of submodules will not be updated.
+	Just like linkgit:git-submodule[1], this will detach the
+	submodules HEAD.
+
+EXAMPLES
+--------
+
+The following command switches to the "master" branch:
+
+------------
+$ git switch master
+------------
+
+After working in the wrong branch, switching to the correct branch
+would be done using:
+
+------------
+$ git switch mytopic
+------------
+
+However, your "wrong" branch and correct "mytopic" branch may differ
+in files that you have modified locally, in which case the above
+switch would fail like this:
+
+------------
+$ git switch mytopic
+error: You have local changes to 'frotz'; not switching branches.
+------------
+
+You can give the `-m` flag to the command, which would try a three-way
+merge:
+
+------------
+$ git switch -m mytopic
+Auto-merging frotz
+------------
+
+After this three-way merge, the local modifications are _not_
+registered in your index file, so `git diff` would show you what
+changes you made since the tip of the new branch.
+
+To switch back to the previous branch before we switched to mytopic
+(i.e. "master" branch):
+
+------------
+$ git switch -
+------------
+
+You can grow a new branch from any commit. For example, switch to
+"HEAD~3" and create branch "fixup":
+
+------------
+$ git switch -c fixup HEAD~3
+Switched to a new branch 'fixup'
+------------
+
+If you want to start a new branch from a remote branch of the same
+name, use `-g`:
+
+------------
+$ git switch -g new-topic
+Branch 'new-topic' set up to track remote branch 'new-topic' from 'origin'
+Switched to a new branch 'new-topic'
+------------
+
+To check out commit "HEAD~3" for temporary inspection or experiment
+without creating a new branch:
+
+------------
+$ git switch --detach HEAD~3
+HEAD is now at 9fc9555312 Merge branch 'cc/shared-index-permbits'
+------------
+
+If it turns out whatever you have done is worth keeping, you can
+always create a new name for it (without switching away):
+
+------------
+$ git switch -c good-surprises
+------------
+
+SEE ALSO
+--------
+linkgit:git-checkout[1]
+
+GIT
+---
+Part of the linkgit:git[1] suite
diff --git a/Documentation/gitattributes.txt b/Documentation/gitattributes.txt
index b8392fc330..5731caa4c6 100644
--- a/Documentation/gitattributes.txt
+++ b/Documentation/gitattributes.txt
@@ -112,7 +112,8 @@ Checking-out and checking-in
 
 These attributes affect how the contents stored in the
 repository are copied to the working tree files when commands
-such as 'git checkout' and 'git merge' run.  They also affect how
+such as 'git switch', 'git checkout'  and 'git merge' run.
+They also affect how
 Git stores the contents you prepare in the working tree in the
 repository upon 'git add' and 'git commit'.
 
diff --git a/Documentation/githooks.txt b/Documentation/githooks.txt
index 959044347e..e257a7810a 100644
--- a/Documentation/githooks.txt
+++ b/Documentation/githooks.txt
@@ -161,12 +161,13 @@ rebased, and is not set when rebasing the current branch.
 post-checkout
 ~~~~~~~~~~~~~
 
-This hook is invoked when a linkgit:git-checkout[1] is run after having updated the
+This hook is invoked when a linkgit:git-checkout[1] or
+linkgit:git-switch[1] is run after having updated the
 worktree.  The hook is given three parameters: the ref of the previous HEAD,
 the ref of the new HEAD (which may or may not have changed), and a flag
 indicating whether the checkout was a branch checkout (changing branches,
 flag=1) or a file checkout (retrieving a file from the index, flag=0).
-This hook cannot affect the outcome of `git checkout`.
+This hook cannot affect the outcome of `git switch` or `git checkout`.
 
 It is also run after linkgit:git-clone[1], unless the `--no-checkout` (`-n`) option is
 used. The first parameter given to the hook is the null-ref, the second the
@@ -402,7 +403,8 @@ exit with a zero status.
 For example, the hook can simply run `git read-tree -u -m HEAD "$1"`
 in order to emulate `git fetch` that is run in the reverse direction
 with `git push`, as the two-tree form of `git read-tree -u -m` is
-essentially the same as `git checkout` that switches branches while
+essentially the same as `git switch` or `git checkout`
+that switches branches while
 keeping the local changes in the working tree that do not interfere
 with the difference between the branches.
 
diff --git a/Makefile b/Makefile
index 6e8d017e8e..0e5b29390c 100644
--- a/Makefile
+++ b/Makefile
@@ -789,6 +789,7 @@ BUILT_INS += git-merge-subtree$X
 BUILT_INS += git-show$X
 BUILT_INS += git-stage$X
 BUILT_INS += git-status$X
+BUILT_INS += git-switch$X
 BUILT_INS += git-whatchanged$X
 
 # what 'all' will build and 'install' will install in gitexecdir,
diff --git a/builtin.h b/builtin.h
index 6538932e99..c64e44450e 100644
--- a/builtin.h
+++ b/builtin.h
@@ -227,6 +227,7 @@ extern int cmd_show_index(int argc, const char **argv, const char *prefix);
 extern int cmd_status(int argc, const char **argv, const char *prefix);
 extern int cmd_stripspace(int argc, const char **argv, const char *prefix);
 extern int cmd_submodule__helper(int argc, const char **argv, const char *prefix);
+extern int cmd_switch(int argc, const char **argv, const char *prefix);
 extern int cmd_symbolic_ref(int argc, const char **argv, const char *prefix);
 extern int cmd_tag(int argc, const char **argv, const char *prefix);
 extern int cmd_tar_tree(int argc, const char **argv, const char *prefix);
diff --git a/builtin/checkout.c b/builtin/checkout.c
index 8ea1349cce..2ac53b4302 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -33,6 +33,11 @@ static const char * const checkout_usage[] = {
 	NULL,
 };
 
+static const char * const switch_branch_usage[] = {
+	N_("git switch [<options>] [<branch>]"),
+	NULL,
+};
+
 struct checkout_opts {
 	int patch_mode;
 	int quiet;
@@ -1396,33 +1401,25 @@ static struct option *add_checkout_path_options(struct checkout_opts *opts,
 	return newopts;
 }
 
-int cmd_checkout(int argc, const char **argv, const char *prefix)
+static int checkout_main(int argc, const char **argv, const char *prefix,
+			 struct checkout_opts *opts, struct option *options,
+			 const char * const usagestr[])
 {
-	struct checkout_opts real_opts;
-	struct checkout_opts *opts = &real_opts;
 	struct branch_info new_branch_info;
 	int dwim_remotes_matched = 0;
 	int dwim_new_local_branch;
-	struct option *options = NULL;
 
-	memset(opts, 0, sizeof(*opts));
 	memset(&new_branch_info, 0, sizeof(new_branch_info));
 	opts->overwrite_ignore = 1;
 	opts->prefix = prefix;
 	opts->show_progress = -1;
 	opts->overlay_mode = -1;
-	opts->no_dwim_new_local_branch = 0;
 
 	git_config(git_checkout_config, opts);
 
 	opts->track = BRANCH_TRACK_UNSPECIFIED;
 
-	options = parse_options_dup(options);
-	options = add_common_options(opts, options);
-	options = add_switch_branch_options(opts, options);
-	options = add_checkout_path_options(opts, options);
-
-	argc = parse_options(argc, argv, prefix, options, checkout_usage,
+	argc = parse_options(argc, argv, prefix, options, usagestr,
 			     PARSE_OPT_KEEP_DASHDASH);
 
 	dwim_new_local_branch = !opts->no_dwim_new_local_branch;
@@ -1555,3 +1552,42 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 		return checkout_branch(opts, &new_branch_info);
 	}
 }
+
+int cmd_checkout(int argc, const char **argv, const char *prefix)
+{
+	struct checkout_opts opts;
+	struct option *options = NULL;
+	int ret;
+
+	memset(&opts, 0, sizeof(opts));
+	opts.no_dwim_new_local_branch = 0;
+
+	options = parse_options_dup(options);
+	options = add_common_options(&opts, options);
+	options = add_switch_branch_options(&opts, options);
+	options = add_checkout_path_options(&opts, options);
+
+	ret = checkout_main(argc, argv, prefix, &opts,
+			    options, checkout_usage);
+	FREE_AND_NULL(options);
+	return ret;
+}
+
+int cmd_switch(int argc, const char **argv, const char *prefix)
+{
+	struct checkout_opts opts;
+	struct option *options = NULL;
+	int ret;
+
+	memset(&opts, 0, sizeof(opts));
+	opts.no_dwim_new_local_branch = 0;
+
+	options = parse_options_dup(options);
+	options = add_common_options(&opts, options);
+	options = add_switch_branch_options(&opts, options);
+
+	ret = checkout_main(argc, argv, prefix, &opts,
+			    options, switch_branch_usage);
+	FREE_AND_NULL(options);
+	return ret;
+}
diff --git a/command-list.txt b/command-list.txt
index 3a9af104b5..13317f47d4 100644
--- a/command-list.txt
+++ b/command-list.txt
@@ -171,6 +171,7 @@ git-status                              mainporcelain           info
 git-stripspace                          purehelpers
 git-submodule                           mainporcelain
 git-svn                                 foreignscminterface
+git-switch                              mainporcelain           history
 git-symbolic-ref                        plumbingmanipulators
 git-tag                                 mainporcelain           history
 git-unpack-file                         plumbinginterrogators
diff --git a/git.c b/git.c
index 0ce0e13f0f..31b8e8d6a1 100644
--- a/git.c
+++ b/git.c
@@ -558,6 +558,7 @@ static struct cmd_struct commands[] = {
 	{ "status", cmd_status, RUN_SETUP | NEED_WORK_TREE },
 	{ "stripspace", cmd_stripspace },
 	{ "submodule--helper", cmd_submodule__helper, RUN_SETUP | SUPPORT_SUPER_PREFIX | NO_PARSEOPT },
+	{ "switch", cmd_switch, RUN_SETUP | NEED_WORK_TREE },
 	{ "symbolic-ref", cmd_symbolic_ref, RUN_SETUP },
 	{ "tag", cmd_tag, RUN_SETUP | DELAY_PAGER_CONFIG },
 	{ "unpack-file", cmd_unpack_file, RUN_SETUP | NO_PARSEOPT },

diff --git a/builtin/checkout.c b/builtin/checkout.c
index 2ac53b4302..f6de232922 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -1353,14 +1353,10 @@ static struct option *add_common_options(struct checkout_opts *opts,
 	return newopts;
 }
 
-static struct option *add_switch_branch_options(struct checkout_opts *opts,
-						struct option *prevopts)
+static struct option *add_common_switch_branch_options(
+	struct checkout_opts *opts, struct option *prevopts)
 {
 	struct option options[] = {
-		OPT_STRING('b', NULL, &opts->new_branch, N_("branch"),
-			   N_("create and checkout a new branch")),
-		OPT_STRING('B', NULL, &opts->new_branch_force, N_("branch"),
-			   N_("create/reset and checkout a branch")),
 		OPT_BOOL('l', NULL, &opts->new_branch_log, N_("create reflog for new branch")),
 		OPT_BOOL(0, "detach", &opts->force_detach, N_("detach HEAD at named commit")),
 		OPT_SET_INT('t', "track",  &opts->track, N_("set upstream info for new branch"),
@@ -1556,15 +1552,22 @@ static int checkout_main(int argc, const char **argv, const char *prefix,
 int cmd_checkout(int argc, const char **argv, const char *prefix)
 {
 	struct checkout_opts opts;
-	struct option *options = NULL;
+	struct option *options;
+	struct option checkout_options[] = {
+		OPT_STRING('b', NULL, &opts.new_branch, N_("branch"),
+			   N_("create and checkout a new branch")),
+		OPT_STRING('B', NULL, &opts.new_branch_force, N_("branch"),
+			   N_("create/reset and checkout a branch")),
+		OPT_END()
+	};
 	int ret;
 
 	memset(&opts, 0, sizeof(opts));
 	opts.no_dwim_new_local_branch = 0;
 
-	options = parse_options_dup(options);
+	options = parse_options_dup(checkout_options);
 	options = add_common_options(&opts, options);
-	options = add_switch_branch_options(&opts, options);
+	options = add_common_switch_branch_options(&opts, options);
 	options = add_checkout_path_options(&opts, options);
 
 	ret = checkout_main(argc, argv, prefix, &opts,
@@ -1577,14 +1580,21 @@ int cmd_switch(int argc, const char **argv, const char *prefix)
 {
 	struct checkout_opts opts;
 	struct option *options = NULL;
+	struct option switch_options[] = {
+		OPT_STRING('c', "create", &opts.new_branch, N_("branch"),
+			   N_("create and switch to a new branch")),
+		OPT_STRING('C', "force-create", &opts.new_branch_force, N_("branch"),
+			   N_("create/reset and switch to a branch")),
+		OPT_END()
+	};
 	int ret;
 
 	memset(&opts, 0, sizeof(opts));
 	opts.no_dwim_new_local_branch = 0;
 
-	options = parse_options_dup(options);
+	options = parse_options_dup(switch_options);
 	options = add_common_options(&opts, options);
-	options = add_switch_branch_options(&opts, options);
+	options = add_common_switch_branch_options(&opts, options);
 
 	ret = checkout_main(argc, argv, prefix, &opts,
 			    options, switch_branch_usage);

diff --git a/builtin/checkout.c b/builtin/checkout.c
index f6de232922..f7d8fa7caa 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -1357,7 +1357,6 @@ static struct option *add_common_switch_branch_options(
 	struct checkout_opts *opts, struct option *prevopts)
 {
 	struct option options[] = {
-		OPT_BOOL('l', NULL, &opts->new_branch_log, N_("create reflog for new branch")),
 		OPT_BOOL(0, "detach", &opts->force_detach, N_("detach HEAD at named commit")),
 		OPT_SET_INT('t', "track",  &opts->track, N_("set upstream info for new branch"),
 			BRANCH_TRACK_EXPLICIT),
@@ -1558,6 +1557,7 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 			   N_("create and checkout a new branch")),
 		OPT_STRING('B', NULL, &opts.new_branch_force, N_("branch"),
 			   N_("create/reset and checkout a branch")),
+		OPT_BOOL('l', NULL, &opts.new_branch_log, N_("create reflog for new branch")),
 		OPT_END()
 	};
 	int ret;

diff --git a/builtin/checkout.c b/builtin/checkout.c
index f7d8fa7caa..4822d5c5d7 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -52,6 +52,7 @@ struct checkout_opts {
 	int count_checkout_paths;
 	int overlay_mode;
 	int no_dwim_new_local_branch;
+	int accept_pathspec;
 
 	/*
 	 * If new checkout options are added, skip_merge_working_tree
@@ -1162,10 +1163,16 @@ static int parse_branchname_arg(int argc, const char **argv,
 	if (!argc)
 		return 0;
 
+	if (!opts->accept_pathspec) {
+		if (argc > 1)
+			die(_("only one reference expected"));
+		has_dash_dash = 1; /* helps disambiguate */
+	}
+
 	arg = argv[0];
 	dash_dash_pos = -1;
 	for (i = 0; i < argc; i++) {
-		if (!strcmp(argv[i], "--")) {
+		if (opts->accept_pathspec && !strcmp(argv[i], "--")) {
 			dash_dash_pos = i;
 			break;
 		}
@@ -1199,11 +1206,12 @@ static int parse_branchname_arg(int argc, const char **argv,
 			recover_with_dwim = 0;
 
 		/*
-		 * Accept "git checkout foo" and "git checkout foo --"
-		 * as candidates for dwim.
+		 * Accept "git checkout foo", "git checkout foo --"
+		 * and "git switch foo" as candidates for dwim.
 		 */
 		if (!(argc == 1 && !has_dash_dash) &&
-		    !(argc == 2 && has_dash_dash))
+		    !(argc == 2 && has_dash_dash) &&
+		    opts->accept_pathspec)
 			recover_with_dwim = 0;
 
 		if (recover_with_dwim) {
@@ -1248,7 +1256,7 @@ static int parse_branchname_arg(int argc, const char **argv,
 		 */
 		if (argc)
 			verify_non_filename(opts->prefix, arg);
-	} else {
+	} else if (opts->accept_pathspec) {
 		argcount++;
 		argv++;
 		argc--;
@@ -1564,6 +1572,7 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 
 	memset(&opts, 0, sizeof(opts));
 	opts.no_dwim_new_local_branch = 0;
+	opts.accept_pathspec = 1;
 
 	options = parse_options_dup(checkout_options);
 	options = add_common_options(&opts, options);
@@ -1591,6 +1600,7 @@ int cmd_switch(int argc, const char **argv, const char *prefix)
 
 	memset(&opts, 0, sizeof(opts));
 	opts.no_dwim_new_local_branch = 0;
+	opts.accept_pathspec = 0;
 
 	options = parse_options_dup(switch_options);
 	options = add_common_options(&opts, options);

diff --git a/builtin/checkout.c b/builtin/checkout.c
index 4822d5c5d7..86e524f7c1 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -53,6 +53,7 @@ struct checkout_opts {
 	int overlay_mode;
 	int no_dwim_new_local_branch;
 	int accept_pathspec;
+	int switch_branch_doing_nothing_is_ok;
 
 	/*
 	 * If new checkout options are added, skip_merge_working_tree
@@ -1319,6 +1320,12 @@ static int checkout_branch(struct checkout_opts *opts,
 		die(_("Cannot switch branch to a non-commit '%s'"),
 		    new_branch_info->name);
 
+	if (!opts->switch_branch_doing_nothing_is_ok &&
+	    !new_branch_info->name &&
+	    !opts->new_branch &&
+	    !opts->force_detach)
+		die(_("missing branch or commit argument"));
+
 	if (new_branch_info->path && !opts->force_detach && !opts->new_branch &&
 	    !opts->ignore_other_worktrees) {
 		int flag;
@@ -1572,6 +1579,7 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 
 	memset(&opts, 0, sizeof(opts));
 	opts.no_dwim_new_local_branch = 0;
+	opts.switch_branch_doing_nothing_is_ok = 1;
 	opts.accept_pathspec = 1;
 
 	options = parse_options_dup(checkout_options);
@@ -1601,6 +1609,7 @@ int cmd_switch(int argc, const char **argv, const char *prefix)
 	memset(&opts, 0, sizeof(opts));
 	opts.no_dwim_new_local_branch = 0;
 	opts.accept_pathspec = 0;
+	opts.switch_branch_doing_nothing_is_ok = 0;
 
 	options = parse_options_dup(switch_options);
 	options = add_common_options(&opts, options);

diff --git a/builtin/checkout.c b/builtin/checkout.c
index 86e524f7c1..d6c968f5f3 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -44,6 +44,7 @@ struct checkout_opts {
 	int merge;
 	int force;
 	int force_detach;
+	int implicit_detach;
 	int writeout_stage;
 	int overwrite_ignore;
 	int ignore_skipworktree;
@@ -1326,6 +1327,14 @@ static int checkout_branch(struct checkout_opts *opts,
 	    !opts->force_detach)
 		die(_("missing branch or commit argument"));
 
+	if (!opts->implicit_detach &&
+	    !opts->force_detach &&
+	    !opts->new_branch &&
+	    !opts->new_branch_force &&
+	    new_branch_info->name &&
+	    !new_branch_info->path)
+		die(_("a branch is expected, got %s"), new_branch_info->name);
+
 	if (new_branch_info->path && !opts->force_detach && !opts->new_branch &&
 	    !opts->ignore_other_worktrees) {
 		int flag;
@@ -1581,6 +1590,7 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 	opts.no_dwim_new_local_branch = 0;
 	opts.switch_branch_doing_nothing_is_ok = 1;
 	opts.accept_pathspec = 1;
+	opts.implicit_detach = 1;
 
 	options = parse_options_dup(checkout_options);
 	options = add_common_options(&opts, options);
@@ -1610,6 +1620,7 @@ int cmd_switch(int argc, const char **argv, const char *prefix)
 	opts.no_dwim_new_local_branch = 0;
 	opts.accept_pathspec = 0;
 	opts.switch_branch_doing_nothing_is_ok = 0;
+	opts.implicit_detach = 0;
 
 	options = parse_options_dup(switch_options);
 	options = add_common_options(&opts, options);

diff --git a/builtin/checkout.c b/builtin/checkout.c
index d6c968f5f3..a5284391a9 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -1381,7 +1381,7 @@ static struct option *add_common_switch_branch_options(
 	struct checkout_opts *opts, struct option *prevopts)
 {
 	struct option options[] = {
-		OPT_BOOL(0, "detach", &opts->force_detach, N_("detach HEAD at named commit")),
+		OPT_BOOL('d', "detach", &opts->force_detach, N_("detach HEAD at named commit")),
 		OPT_SET_INT('t', "track",  &opts->track, N_("set upstream info for new branch"),
 			BRANCH_TRACK_EXPLICIT),
 		OPT_STRING(0, "orphan", &opts->new_orphan_branch, N_("new-branch"), N_("new unparented branch")),

Documentation/git-checkout.txt, builtin/checkout.c

diff --git a/Documentation/git-checkout.txt b/Documentation/git-checkout.txt
index 31c6cbef19..bcb7822c27 100644
--- a/Documentation/git-checkout.txt
+++ b/Documentation/git-checkout.txt
@@ -31,22 +31,13 @@ branch.
 	<branch>.
 +
 If <branch> is not found but there does exist a tracking branch in
-exactly one remote (call it <remote>) with a matching name, treat as
-equivalent to
+exactly one remote (call it <remote>) with a matching name and
+--no-guess is not specified, treat as equivalent to
 +
 ------------
 $ git checkout -b <branch> --track <remote>/<branch>
 ------------
 +
-If the branch exists in multiple remotes and one of them is named by
-the `checkout.defaultRemote` configuration variable, we'll use that
-one for the purposes of disambiguation, even if the `<branch>` isn't
-unique across all remotes. Set it to
-e.g. `checkout.defaultRemote=origin` to always checkout remote
-branches from there if `<branch>` is ambiguous but exists on the
-'origin' remote. See also `checkout.defaultRemote` in
-linkgit:git-config[1].
-+
 You could omit <branch>, in which case the command degenerates to
 "check out the current branch", which is a glorified no-op with
 rather expensive side-effects to show only the tracking information,
@@ -182,6 +173,26 @@ explicitly give a name with `-b` in such a case.
 	Do not set up "upstream" configuration, even if the
 	branch.autoSetupMerge configuration variable is true.
 
+--[no-]guess::
+	If <branch> is not found but there does exist a tracking
+	branch in exactly one remote (call it <remote>) with a
+	matching name, treat as equivalent to
++
+------------
+$ git checkout -b <branch> --track <remote>/<branch>
+------------
++
+If the branch exists in multiple remotes and one of them is named by
+the `checkout.defaultRemote` configuration variable, we'll use that
+one for the purposes of disambiguation, even if the `<branch>` isn't
+unique across all remotes. Set it to
+e.g. `checkout.defaultRemote=origin` to always checkout remote
+branches from there if `<branch>` is ambiguous but exists on the
+'origin' remote. See also `checkout.defaultRemote` in
+linkgit:git-config[1].
++
+Use `--no-guess` to disable this.
+
 -l::
 	Create the new branch's reflog; see linkgit:git-branch[1] for
 	details.
@@ -284,10 +295,6 @@ Note that this option uses the no overlay mode by default (see also
 	Just like linkgit:git-submodule[1], this will detach the
 	submodules HEAD.
 
---no-guess::
-	Do not attempt to create a branch if a remote tracking branch
-	of the same name exists.
-
 --[no-]overlay::
 	In the default overlay mode, `git checkout` never
 	removes files from the index or the working tree.  When
diff --git a/builtin/checkout.c b/builtin/checkout.c
index a5284391a9..a49ab35b7d 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -52,7 +52,7 @@ struct checkout_opts {
 	int show_progress;
 	int count_checkout_paths;
 	int overlay_mode;
-	int no_dwim_new_local_branch;
+	int dwim_new_local_branch;
 	int accept_pathspec;
 	int switch_branch_doing_nothing_is_ok;
 
@@ -1388,8 +1388,6 @@ static struct option *add_common_switch_branch_options(
 		OPT_BOOL_F(0, "overwrite-ignore", &opts->overwrite_ignore,
 			   N_("update ignored files (default)"),
 			   PARSE_OPT_NOCOMPLETE),
-		OPT_BOOL(0, "no-guess", &opts->no_dwim_new_local_branch,
-			 N_("second guess 'git checkout <no-such-branch>'")),
 		OPT_BOOL(0, "ignore-other-worktrees", &opts->ignore_other_worktrees,
 			 N_("do not check if another worktree is holding the given ref")),
 		OPT_END()
@@ -1426,7 +1424,6 @@ static int checkout_main(int argc, const char **argv, const char *prefix,
 {
 	struct branch_info new_branch_info;
 	int dwim_remotes_matched = 0;
-	int dwim_new_local_branch;
 
 	memset(&new_branch_info, 0, sizeof(new_branch_info));
 	opts->overwrite_ignore = 1;
@@ -1441,7 +1438,6 @@ static int checkout_main(int argc, const char **argv, const char *prefix,
 	argc = parse_options(argc, argv, prefix, options, usagestr,
 			     PARSE_OPT_KEEP_DASHDASH);
 
-	dwim_new_local_branch = !opts->no_dwim_new_local_branch;
 	if (opts->show_progress < 0) {
 		if (opts->quiet)
 			opts->show_progress = 0;
@@ -1501,7 +1497,7 @@ static int checkout_main(int argc, const char **argv, const char *prefix,
 		struct object_id rev;
 		int dwim_ok =
 			!opts->patch_mode &&
-			dwim_new_local_branch &&
+			opts->dwim_new_local_branch &&
 			opts->track == BRANCH_TRACK_UNSPECIFIED &&
 			!opts->new_branch;
 		int n = parse_branchname_arg(argc, argv, dwim_ok,
@@ -1582,12 +1578,14 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 		OPT_STRING('B', NULL, &opts.new_branch_force, N_("branch"),
 			   N_("create/reset and checkout a branch")),
 		OPT_BOOL('l', NULL, &opts.new_branch_log, N_("create reflog for new branch")),
+		OPT_BOOL(0, "guess", &opts.dwim_new_local_branch,
+			 N_("second guess 'git checkout <no-such-branch>' (default)")),
 		OPT_END()
 	};
 	int ret;
 
 	memset(&opts, 0, sizeof(opts));
-	opts.no_dwim_new_local_branch = 0;
+	opts.dwim_new_local_branch = 1;
 	opts.switch_branch_doing_nothing_is_ok = 1;
 	opts.accept_pathspec = 1;
 	opts.implicit_detach = 1;
@@ -1612,12 +1610,14 @@ int cmd_switch(int argc, const char **argv, const char *prefix)
 			   N_("create and switch to a new branch")),
 		OPT_STRING('C', "force-create", &opts.new_branch_force, N_("branch"),
 			   N_("create/reset and switch to a branch")),
+		OPT_BOOL('g', "guess", &opts.dwim_new_local_branch,
+			 N_("second guess 'git switch <no-such-branch>'")),
 		OPT_END()
 	};
 	int ret;
 
 	memset(&opts, 0, sizeof(opts));
-	opts.no_dwim_new_local_branch = 0;
+	opts.dwim_new_local_branch = 0;
 	opts.accept_pathspec = 0;
 	opts.switch_branch_doing_nothing_is_ok = 0;
 	opts.implicit_detach = 0;

Documentation/config/checkout.txt, builtin/checkout.c, t/t1090-sparse-checkout-scope.sh

diff --git a/Documentation/config/checkout.txt b/Documentation/config/checkout.txt
index fc211eca58..2fe24049fe 100644
--- a/Documentation/config/checkout.txt
+++ b/Documentation/config/checkout.txt
@@ -17,14 +17,6 @@ and by linkgit:git-worktree[1] when 'git worktree add' refers to a
 remote branch. This setting might be used for other checkout-like
 commands or functionality in the future.
 
-checkout.optimizeNewBranch::
-	Optimizes the performance of "git checkout -b <new_branch>" when
-	using sparse-checkout.  When set to true, git will not update the
-	repo based on the current sparse-checkout settings.  This means it
-	will not update the skip-worktree bit in the index nor add/remove
-	files in the working directory to reflect the current sparse checkout
-	settings nor will it show the local changes.
-
 checkout.overlayMode::
 	In the default overlay mode, `git checkout` never
 	removes files from the index or the working tree.  When
diff --git a/builtin/checkout.c b/builtin/checkout.c
index a49ab35b7d..21a3fe3fb8 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -25,8 +25,6 @@
 #include "submodule.h"
 #include "advice.h"
 
-static int checkout_optimize_new_branch;
-
 static const char * const checkout_usage[] = {
 	N_("git checkout [<options>] <branch>"),
 	N_("git checkout [<options>] [<branch>] -- <file>..."),
@@ -55,11 +53,7 @@ struct checkout_opts {
 	int dwim_new_local_branch;
 	int accept_pathspec;
 	int switch_branch_doing_nothing_is_ok;
-
-	/*
-	 * If new checkout options are added, skip_merge_working_tree
-	 * should be updated accordingly.
-	 */
+	int only_merge_on_switching_branches;
 
 	const char *new_branch;
 	const char *new_branch_force;
@@ -556,104 +550,6 @@ static void setup_branch_path(struct branch_info *branch)
 	branch->path = strbuf_detach(&buf, NULL);
 }
 
-/*
- * Skip merging the trees, updating the index and working directory if and
- * only if we are creating a new branch via "git checkout -b <new_branch>."
- */
-static int skip_merge_working_tree(const struct checkout_opts *opts,
-	const struct branch_info *old_branch_info,
-	const struct branch_info *new_branch_info)
-{
-	/*
-	 * Do the merge if sparse checkout is on and the user has not opted in
-	 * to the optimized behavior
-	 */
-	if (core_apply_sparse_checkout && !checkout_optimize_new_branch)
-		return 0;
-
-	/*
-	 * We must do the merge if we are actually moving to a new commit.
-	 */
-	if (!old_branch_info->commit || !new_branch_info->commit ||
-		!oideq(&old_branch_info->commit->object.oid,
-		       &new_branch_info->commit->object.oid))
-		return 0;
-
-	/*
-	 * opts->patch_mode cannot be used with switching branches so is
-	 * not tested here
-	 */
-
-	/*
-	 * opts->quiet only impacts output so doesn't require a merge
-	 */
-
-	/*
-	 * Honor the explicit request for a three-way merge or to throw away
-	 * local changes
-	 */
-	if (opts->merge || opts->force)
-		return 0;
-
-	/*
-	 * --detach is documented as "updating the index and the files in the
-	 * working tree" but this optimization skips those steps so fall through
-	 * to the regular code path.
-	 */
-	if (opts->force_detach)
-		return 0;
-
-	/*
-	 * opts->writeout_stage cannot be used with switching branches so is
-	 * not tested here
-	 */
-
-	/*
-	 * Honor the explicit ignore requests
-	 */
-	if (!opts->overwrite_ignore || opts->ignore_skipworktree ||
-		opts->ignore_other_worktrees)
-		return 0;
-
-	/*
-	 * opts->show_progress only impacts output so doesn't require a merge
-	 */
-
-	/*
-	 * opts->overlay_mode cannot be used with switching branches so is
-	 * not tested here
-	 */
-
-	/*
-	 * If we aren't creating a new branch any changes or updates will
-	 * happen in the existing branch.  Since that could only be updating
-	 * the index and working directory, we don't want to skip those steps
-	 * or we've defeated any purpose in running the command.
-	 */
-	if (!opts->new_branch)
-		return 0;
-
-	/*
-	 * new_branch_force is defined to "create/reset and checkout a branch"
-	 * so needs to go through the merge to do the reset
-	 */
-	if (opts->new_branch_force)
-		return 0;
-
-	/*
-	 * A new orphaned branch requrires the index and the working tree to be
-	 * adjusted to <start_point>
-	 */
-	if (opts->new_orphan_branch)
-		return 0;
-
-	/*
-	 * Remaining variables are not checkout options but used to track state
-	 */
-
-	return 1;
-}
-
 static int merge_working_tree(const struct checkout_opts *opts,
 			      struct branch_info *old_branch_info,
 			      struct branch_info *new_branch_info,
@@ -1011,6 +907,8 @@ static int switch_branches(const struct checkout_opts *opts,
 	void *path_to_free;
 	struct object_id rev;
 	int flag, writeout_error = 0;
+	int do_merge = 1;
+
 	memset(&old_branch_info, 0, sizeof(old_branch_info));
 	old_branch_info.path = path_to_free = resolve_refdup("HEAD", 0, &rev, &flag);
 	if (old_branch_info.path)
@@ -1027,16 +925,12 @@ static int switch_branches(const struct checkout_opts *opts,
 		if (!new_branch_info->commit)
 			die(_("You are on a branch yet to be born"));
 		parse_commit_or_die(new_branch_info->commit);
+
+		if (opts->only_merge_on_switching_branches)
+			do_merge = 0;
 	}
 
-	/* optimize the "checkout -b <new_branch> path */
-	if (skip_merge_working_tree(opts, &old_branch_info, new_branch_info)) {
-		if (!checkout_optimize_new_branch && !opts->quiet) {
-			if (read_cache_preload(NULL) < 0)
-				return error(_("index file corrupt"));
-			show_local_changes(&new_branch_info->commit->object, &opts->diff_options);
-		}
-	} else {
+	if (do_merge) {
 		ret = merge_working_tree(opts, &old_branch_info, new_branch_info, &writeout_error);
 		if (ret) {
 			free(path_to_free);
@@ -1058,11 +952,6 @@ static int git_checkout_config(const char *var, const char *value, void *cb)
 {
 	struct checkout_opts *opts = cb;
 
-	if (!strcmp(var, "checkout.optimizenewbranch")) {
-		checkout_optimize_new_branch = git_config_bool(var, value);
-		return 0;
-	}
-
 	if (!strcmp(var, "checkout.overlaymode")) {
 		opts->overlay_mode = git_config_bool(var, value);
 		return 0;
@@ -1587,6 +1476,7 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 	memset(&opts, 0, sizeof(opts));
 	opts.dwim_new_local_branch = 1;
 	opts.switch_branch_doing_nothing_is_ok = 1;
+	opts.only_merge_on_switching_branches = 0;
 	opts.accept_pathspec = 1;
 	opts.implicit_detach = 1;
 
@@ -1620,6 +1510,7 @@ int cmd_switch(int argc, const char **argv, const char *prefix)
 	opts.dwim_new_local_branch = 0;
 	opts.accept_pathspec = 0;
 	opts.switch_branch_doing_nothing_is_ok = 0;
+	opts.only_merge_on_switching_branches = 1;
 	opts.implicit_detach = 0;
 
 	options = parse_options_dup(switch_options);
diff --git a/t/t1090-sparse-checkout-scope.sh b/t/t1090-sparse-checkout-scope.sh
index 090b7fc3d3..40cc004326 100755
--- a/t/t1090-sparse-checkout-scope.sh
+++ b/t/t1090-sparse-checkout-scope.sh
@@ -31,20 +31,6 @@ test_expect_success 'perform sparse checkout of master' '
 	test_path_is_file c
 '
 
-test_expect_success 'checkout -b checkout.optimizeNewBranch interaction' '
-	cp .git/info/sparse-checkout .git/info/sparse-checkout.bak &&
-	test_when_finished "
-		mv -f .git/info/sparse-checkout.bak .git/info/sparse-checkout
-		git checkout master
-	" &&
-	echo "/b" >>.git/info/sparse-checkout &&
-	test "$(git ls-files -t b)" = "S b" &&
-	git -c checkout.optimizeNewBranch=true checkout -b fast &&
-	test "$(git ls-files -t b)" = "S b" &&
-	git checkout -b slow &&
-	test "$(git ls-files -t b)" = "H b"
-'
-
 test_expect_success 'merge feature branch into sparse checkout of master' '
 	git merge feature &&
 	test_path_is_file a &&

diff --git a/t/t2060-switch.sh b/t/t2060-switch.sh
new file mode 100755
index 0000000000..1e1e834c1b
--- /dev/null
+++ b/t/t2060-switch.sh
@@ -0,0 +1,87 @@
+#!/bin/sh
+
+test_description='switch basic functionality'
+
+. ./test-lib.sh
+
+test_expect_success 'setup' '
+	test_commit first &&
+	git branch first-branch &&
+	test_commit second &&
+	test_commit third &&
+	git remote add origin nohost:/nopath &&
+	git update-ref refs/remotes/origin/foo first-branch
+'
+
+test_expect_success 'switch branch no arguments' '
+	test_must_fail git switch
+'
+
+test_expect_success 'switch branch' '
+	git switch first-branch &&
+	test_path_is_missing second.t
+'
+
+test_expect_success 'switch to a commit' '
+	test_must_fail git switch master^{commit}
+'
+
+test_expect_success 'switch and detach' '
+	test_when_finished git switch master &&
+	git switch --detach master^{commit} &&
+	test_must_fail git symbolic-ref HEAD
+'
+
+test_expect_success 'switch and detach current branch' '
+	test_when_finished git switch master &&
+	git switch master &&
+	git switch --detach &&
+	test_must_fail git symbolic-ref HEAD
+'
+
+test_expect_success 'switch and create branch' '
+	test_when_finished git switch master &&
+	git switch -c temp master^ &&
+	test_cmp_rev master^ refs/heads/temp &&
+	echo refs/heads/temp >expected-branch &&
+	git symbolic-ref HEAD >actual-branch &&
+	test_cmp expected-branch actual-branch
+'
+
+test_expect_success 'force create branch from HEAD' '
+	test_when_finished git switch master &&
+	git switch --detach master &&
+	git switch -C temp &&
+	test_cmp_rev master refs/heads/temp &&
+	echo refs/heads/temp >expected-branch &&
+	git symbolic-ref HEAD >actual-branch &&
+	test_cmp expected-branch actual-branch
+'
+
+test_expect_success 'new orphan branch' '
+	test_when_finished git switch master &&
+	git switch --orphan new-orphan master^ &&
+	test_commit orphan &&
+	git cat-file commit refs/heads/new-orphan >commit &&
+	! grep ^parent commit
+'
+
+test_expect_success 'switching ignores file of same branch name' '
+	test_when_finished git switch master &&
+	: >first-branch &&
+	git switch first-branch &&
+	echo refs/heads/first-branch >expected &&
+	git symbolic-ref HEAD >actual &&
+	test_commit expected actual
+'
+
+test_expect_success 'guess and create branch ' '
+	test_when_finished git switch master &&
+	test_must_fail git switch foo &&
+	git switch --guess foo &&
+	echo refs/heads/foo >expected &&
+	git symbolic-ref HEAD >actual &&
+	test_cmp expected actual
+'
+
+test_done

diff --git a/contrib/completion/git-completion.bash b/contrib/completion/git-completion.bash
index 499e56f83d..891abb72d7 100644
--- a/contrib/completion/git-completion.bash
+++ b/contrib/completion/git-completion.bash
@@ -2126,6 +2126,32 @@ _git_status ()
 	__git_complete_index_file "$complete_opt"
 }
 
+_git_switch ()
+{
+	case "$cur" in
+	--conflict=*)
+		__gitcomp "diff3 merge" "" "${cur##--conflict=}"
+		;;
+	--*)
+		__gitcomp_builtin switch
+		;;
+	*)
+		# check if ---guess was specified to enable DWIM mode
+		local track_opt= only_local_ref=n
+		if [ -n "$(__git_find_on_cmdline "-g --guess")" ]; then
+			track_opt='--track'
+		elif [ -z "$(__git_find_on_cmdline "-d --detach")" ]; then
+			only_local_ref=y
+		fi
+		if [ $only_local_ref = y ]; then
+			__gitcomp_direct "$(__git_heads "" "$cur" " ")"
+		else
+			__git_complete_refs $track_opt
+		fi
+		;;
+	esac
+}
+
 __git_config_get_set_variables ()
 {
 	local prevword word config_file= c=$cword

Documentation/git-branch.txt, Documentation/git-check-ref-format.txt, Documentation/git-format-patch.txt, Documentation/git-merge-base.txt, Documentation/git-rebase.txt, Documentation/git-remote.txt, Documentation/git-rerere.txt, Documentation/git-reset.txt, Documentation/git-stash.txt, Documentation/gitcore-tutorial.txt, Documentation/giteveryday.txt, Documentation/gittutorial.txt, Documentation/revisions.txt, Documentation/user-manual.txt, advice.c, sha1-name.c, t/t2020-checkout-detach.sh

diff --git a/Documentation/git-branch.txt b/Documentation/git-branch.txt
index bf5316ffa9..3cf6153415 100644
--- a/Documentation/git-branch.txt
+++ b/Documentation/git-branch.txt
@@ -48,7 +48,7 @@ The command's second form creates a new branch head named <branchname>
 which points to the current `HEAD`, or <start-point> if given.
 
 Note that this will create the new branch, but it will not switch the
-working tree to it; use "git checkout <newbranch>" to switch to the
+working tree to it; use "git switch <newbranch>" to switch to the
 new branch.
 
 When a local branch is started off a remote-tracking branch, Git sets up the
@@ -194,7 +194,7 @@ This option is only applicable in non-verbose mode.
 +
 This behavior is the default when the start point is a remote-tracking branch.
 Set the branch.autoSetupMerge configuration variable to `false` if you
-want `git checkout` and `git branch` to always behave as if `--no-track`
+want `git switch`, `git checkout` and `git branch` to always behave as if `--no-track`
 were given. Set it to `always` if you want this behavior when the
 start-point is either a local or remote-tracking branch.
 
@@ -293,7 +293,7 @@ Start development from a known tag::
 $ git clone git://git.kernel.org/pub/scm/.../linux-2.6 my2.6
 $ cd my2.6
 $ git branch my2.6.14 v2.6.14   <1>
-$ git checkout my2.6.14
+$ git switch my2.6.14
 ------------
 +
 <1> This step and the next one could be combined into a single step with
@@ -318,9 +318,9 @@ is currently checked out) does not have all commits from the test branch.
 NOTES
 -----
 
-If you are creating a branch that you want to checkout immediately, it is
-easier to use the git checkout command with its `-b` option to create
-a branch and check it out with a single command.
+If you are creating a branch that you want to switch to immediately,
+it is easier to use the "git switch" command with its `-c` option to
+do the same thing with a single command.
 
 The options `--contains`, `--no-contains`, `--merged` and `--no-merged`
 serve four related but different purposes:
diff --git a/Documentation/git-check-ref-format.txt b/Documentation/git-check-ref-format.txt
index d9de992585..ee6a4144fb 100644
--- a/Documentation/git-check-ref-format.txt
+++ b/Documentation/git-check-ref-format.txt
@@ -88,7 +88,8 @@ but it is explicitly forbidden at the beginning of a branch name).
 When run with `--branch` option in a repository, the input is first
 expanded for the ``previous checkout syntax''
 `@{-n}`.  For example, `@{-1}` is a way to refer the last thing that
-was checked out using "git checkout" operation. This option should be
+was checked out using "git switch" or "git checkout" operation.
+This option should be
 used by porcelains to accept this syntax anywhere a branch name is
 expected, so they can act as if you typed the branch name. As an
 exception note that, the ``previous checkout operation'' might result
diff --git a/Documentation/git-format-patch.txt b/Documentation/git-format-patch.txt
index 27304428a1..3d42853529 100644
--- a/Documentation/git-format-patch.txt
+++ b/Documentation/git-format-patch.txt
@@ -421,7 +421,7 @@ One way to test if your MUA is set up correctly is:
 * Apply it:
 
     $ git fetch <project> master:test-apply
-    $ git checkout test-apply
+    $ git switch test-apply
     $ git reset --hard
     $ git am a.patch
 
diff --git a/Documentation/git-merge-base.txt b/Documentation/git-merge-base.txt
index 9f07f4f6ed..261d5c1164 100644
--- a/Documentation/git-merge-base.txt
+++ b/Documentation/git-merge-base.txt
@@ -149,7 +149,7 @@ instead.
 Discussion on fork-point mode
 -----------------------------
 
-After working on the `topic` branch created with `git checkout -b
+After working on the `topic` branch created with `git switch -c
 topic origin/master`, the history of remote-tracking branch
 `origin/master` may have been rewound and rebuilt, leading to a
 history of this shape:
diff --git a/Documentation/git-rebase.txt b/Documentation/git-rebase.txt
index 4dd5853d6e..420777c10b 100644
--- a/Documentation/git-rebase.txt
+++ b/Documentation/git-rebase.txt
@@ -17,7 +17,7 @@ SYNOPSIS
 DESCRIPTION
 -----------
 If <branch> is specified, 'git rebase' will perform an automatic
-`git checkout <branch>` before doing anything else.  Otherwise
+`git switch <branch>` before doing anything else.  Otherwise
 it remains on the current branch.
 
 If <upstream> is not specified, the upstream configured in
diff --git a/Documentation/git-remote.txt b/Documentation/git-remote.txt
index 0cad37fb81..9659abbf8e 100644
--- a/Documentation/git-remote.txt
+++ b/Documentation/git-remote.txt
@@ -230,7 +230,7 @@ $ git branch -r
   staging/master
   staging/staging-linus
   staging/staging-next
-$ git checkout -b staging staging/master
+$ git switch -c staging staging/master
 ...
 ------------
 
diff --git a/Documentation/git-rerere.txt b/Documentation/git-rerere.txt
index df310d2a58..fe4434ad9d 100644
--- a/Documentation/git-rerere.txt
+++ b/Documentation/git-rerere.txt
@@ -91,7 +91,7 @@ For such a test, you need to merge master and topic somehow.
 One way to do it is to pull master into the topic branch:
 
 ------------
-	$ git checkout topic
+	$ git switch topic
 	$ git merge master
 
               o---*---o---+ topic
@@ -113,10 +113,10 @@ the upstream might have been advanced since the test merge `+`,
 in which case the final commit graph would look like this:
 
 ------------
-	$ git checkout topic
+	$ git switch topic
 	$ git merge master
 	$ ... work on both topic and master branches
-	$ git checkout master
+	$ git switch master
 	$ git merge topic
 
               o---*---o---+---o---o topic
@@ -136,11 +136,11 @@ merges, you could blow away the test merge, and keep building on
 top of the tip before the test merge:
 
 ------------
-	$ git checkout topic
+	$ git switch topic
 	$ git merge master
 	$ git reset --hard HEAD^ ;# rewind the test merge
 	$ ... work on both topic and master branches
-	$ git checkout master
+	$ git switch master
 	$ git merge topic
 
               o---*---o-------o---o topic
diff --git a/Documentation/git-reset.txt b/Documentation/git-reset.txt
index 9f69ae8b69..020ba838c9 100644
--- a/Documentation/git-reset.txt
+++ b/Documentation/git-reset.txt
@@ -149,9 +149,9 @@ See also the `--amend` option to linkgit:git-commit[1].
 Undo a commit, making it a topic branch::
 +
 ------------
-$ git branch topic/wip     <1>
-$ git reset --hard HEAD~3  <2>
-$ git checkout topic/wip   <3>
+$ git branch topic/wip          <1>
+$ git reset --hard HEAD~3       <2>
+$ git switch topic/wip          <3>
 ------------
 +
 <1> You have made some commits, but realize they were premature
@@ -232,13 +232,13 @@ working tree are not in any shape to be committed yet, but you
 need to get to the other branch for a quick bugfix.
 +
 ------------
-$ git checkout feature ;# you were working in "feature" branch and
-$ work work work       ;# got interrupted
+$ git switch feature  ;# you were working in "feature" branch and
+$ work work work      ;# got interrupted
 $ git commit -a -m "snapshot WIP"                 <1>
-$ git checkout master
+$ git switch master
 $ fix fix fix
 $ git commit ;# commit with real log
-$ git checkout feature
+$ git switch feature
 $ git reset --soft HEAD^ ;# go back to WIP state  <2>
 $ git reset                                       <3>
 ------------
@@ -279,18 +279,18 @@ reset it while keeping the changes in your working tree.
 +
 ------------
 $ git tag start
-$ git checkout -b branch1
+$ git switch -c branch1
 $ edit
 $ git commit ...                            <1>
 $ edit
-$ git checkout -b branch2                   <2>
+$ git switch -c branch2                     <2>
 $ git reset --keep start                    <3>
 ------------
 +
 <1> This commits your first edits in `branch1`.
 <2> In the ideal world, you could have realized that the earlier
     commit did not belong to the new topic when you created and switched
-    to `branch2` (i.e. `git checkout -b branch2 start`), but nobody is
+    to `branch2` (i.e. `git switch -c branch2 start`), but nobody is
     perfect.
 <3> But you can use `reset --keep` to remove the unwanted commit after
     you switched to `branch2`.
diff --git a/Documentation/git-stash.txt b/Documentation/git-stash.txt
index 7ef8c47911..ebb6282db3 100644
--- a/Documentation/git-stash.txt
+++ b/Documentation/git-stash.txt
@@ -235,12 +235,12 @@ return to your original branch to make the emergency fix, like this:
 +
 ----------------------------------------------------------------
 # ... hack hack hack ...
-$ git checkout -b my_wip
+$ git switch -c my_wip
 $ git commit -a -m "WIP"
-$ git checkout master
+$ git switch master
 $ edit emergency fix
 $ git commit -a -m "Fix in a hurry"
-$ git checkout my_wip
+$ git switch my_wip
 $ git reset --soft HEAD^
 # ... continue hacking ...
 ----------------------------------------------------------------
@@ -293,7 +293,8 @@ SEE ALSO
 linkgit:git-checkout[1],
 linkgit:git-commit[1],
 linkgit:git-reflog[1],
-linkgit:git-reset[1]
+linkgit:git-reset[1],
+linkgit:git-switch[1]
 
 GIT
 ---
diff --git a/Documentation/gitcore-tutorial.txt b/Documentation/gitcore-tutorial.txt
index e29a9effcc..6bd0f192cc 100644
--- a/Documentation/gitcore-tutorial.txt
+++ b/Documentation/gitcore-tutorial.txt
@@ -741,7 +741,7 @@ used earlier, and create a branch in it. You do that by simply just
 saying that you want to check out a new branch:
 
 ------------
-$ git checkout -b mybranch
+$ git switch -c mybranch
 ------------
 
 will create a new branch based at the current `HEAD` position, and switch
@@ -755,7 +755,7 @@ just telling 'git checkout' what the base of the checkout would be.
 In other words, if you have an earlier tag or branch, you'd just do
 
 ------------
-$ git checkout -b mybranch earlier-commit
+$ git switch -c mybranch earlier-commit
 ------------
 
 and it would create the new branch `mybranch` at the earlier commit,
@@ -765,7 +765,7 @@ and check out the state at that time.
 You can always just jump back to your original `master` branch by doing
 
 ------------
-$ git checkout master
+$ git switch master
 ------------
 
 (or any other branch-name, for that matter) and if you forget which
@@ -794,7 +794,7 @@ $ git branch <branchname> [startingpoint]
 
 which will simply _create_ the branch, but will not do anything further.
 You can then later -- once you decide that you want to actually develop
-on that branch -- switch to that branch with a regular 'git checkout'
+on that branch -- switch to that branch with a regular 'git switch'
 with the branchname as the argument.
 
 
@@ -808,7 +808,7 @@ being the same as the original `master` branch, let's make sure we're in
 that branch, and do some work there.
 
 ------------------------------------------------
-$ git checkout mybranch
+$ git switch mybranch
 $ echo "Work, work, work" >>hello
 $ git commit -m "Some work." -i hello
 ------------------------------------------------
@@ -825,7 +825,7 @@ does some work in the original branch, and simulate that by going back
 to the master branch, and editing the same file differently there:
 
 ------------
-$ git checkout master
+$ git switch master
 ------------
 
 Here, take a moment to look at the contents of `hello`, and notice how they
@@ -958,7 +958,7 @@ to the `master` branch. Let's go back to `mybranch`, and run
 'git merge' to get the "upstream changes" back to your branch.
 
 ------------
-$ git checkout mybranch
+$ git switch mybranch
 $ git merge -m "Merge upstream changes." master
 ------------
 
@@ -1133,9 +1133,9 @@ Remember, before running 'git merge', our `master` head was at
 work." commit.
 
 ------------
-$ git checkout mybranch
+$ git switch mybranch
 $ git reset --hard master^2
-$ git checkout master
+$ git switch master
 $ git reset --hard master^
 ------------
 
diff --git a/Documentation/giteveryday.txt b/Documentation/giteveryday.txt
index 9f2528fc8c..38015026bb 100644
--- a/Documentation/giteveryday.txt
+++ b/Documentation/giteveryday.txt
@@ -41,7 +41,7 @@ following commands.
 
   * linkgit:git-log[1] to see what happened.
 
-  * linkgit:git-checkout[1] and linkgit:git-branch[1] to switch
+  * linkgit:git-switch[1] and linkgit:git-branch[1] to switch
     branches.
 
   * linkgit:git-add[1] to manage the index file.
@@ -80,7 +80,7 @@ $ git tag v2.43 <2>
 Create a topic branch and develop.::
 +
 ------------
-$ git checkout -b alsa-audio <1>
+$ git switch -c alsa-audio <1>
 $ edit/compile/test
 $ git checkout -- curses/ux_audio_oss.c <2>
 $ git add curses/ux_audio_alsa.c <3>
@@ -90,7 +90,7 @@ $ git commit -a -s <5>
 $ edit/compile/test
 $ git diff HEAD^ <6>
 $ git commit -a --amend <7>
-$ git checkout master <8>
+$ git switch master <8>
 $ git merge alsa-audio <9>
 $ git log --since='3 days ago' <10>
 $ git log v2.43.. curses/ <11>
@@ -148,11 +148,11 @@ Clone the upstream and work on it.  Feed changes to upstream.::
 ------------
 $ git clone git://git.kernel.org/pub/scm/.../torvalds/linux-2.6 my2.6
 $ cd my2.6
-$ git checkout -b mine master <1>
+$ git switch -c mine master <1>
 $ edit/compile/test; git commit -a -s <2>
 $ git format-patch master <3>
 $ git send-email --to="person <email@example.com>" 00*.patch <4>
-$ git checkout master <5>
+$ git switch master <5>
 $ git pull <6>
 $ git log -p ORIG_HEAD.. arch/i386 include/asm-i386 <7>
 $ git ls-remote --heads http://git.kernel.org/.../jgarzik/libata-dev.git <8>
@@ -194,7 +194,7 @@ satellite$ edit/compile/test/commit
 satellite$ git push origin <4>
 
 mothership$ cd frotz
-mothership$ git checkout master
+mothership$ git switch master
 mothership$ git merge satellite/master <5>
 ------------
 +
@@ -216,7 +216,7 @@ machine into the master branch.
 Branch off of a specific tag.::
 +
 ------------
-$ git checkout -b private2.6.14 v2.6.14 <1>
+$ git switch -c private2.6.14 v2.6.14 <1>
 $ edit/compile/test; git commit -a
 $ git checkout master
 $ git cherry-pick v2.6.14..private2.6.14 <2>
@@ -274,14 +274,14 @@ $ mailx <3>
 & s 2 3 4 5 ./+to-apply
 & s 7 8 ./+hold-linus
 & q
-$ git checkout -b topic/one master
+$ git switch -c topic/one master
 $ git am -3 -i -s ./+to-apply <4>
 $ compile/test
-$ git checkout -b hold/linus && git am -3 -i -s ./+hold-linus <5>
-$ git checkout topic/one && git rebase master <6>
-$ git checkout pu && git reset --hard next <7>
+$ git switch -c hold/linus && git am -3 -i -s ./+hold-linus <5>
+$ git switch topic/one && git rebase master <6>
+$ git switch pu && git reset --hard next <7>
 $ git merge topic/one topic/two && git merge hold/linus <8>
-$ git checkout maint
+$ git switch maint
 $ git cherry-pick master~4 <9>
 $ compile/test
 $ git tag -s -m "GIT 0.99.9x" v0.99.9x <10>
diff --git a/Documentation/gittutorial.txt b/Documentation/gittutorial.txt
index 242de31cb6..e6ad6b5f8d 100644
--- a/Documentation/gittutorial.txt
+++ b/Documentation/gittutorial.txt
@@ -207,7 +207,7 @@ automatically.  The asterisk marks the branch you are currently on;
 type
 
 ------------------------------------------------
-$ git checkout experimental
+$ git switch experimental
 ------------------------------------------------
 
 to switch to the experimental branch.  Now edit a file, commit the
@@ -216,7 +216,7 @@ change, and switch back to the master branch:
 ------------------------------------------------
 (edit file)
 $ git commit -a
-$ git checkout master
+$ git switch master
 ------------------------------------------------
 
 Check that the change you made is no longer visible, since it was
diff --git a/Documentation/revisions.txt b/Documentation/revisions.txt
index 72daa20e76..a1c7a65da6 100644
--- a/Documentation/revisions.txt
+++ b/Documentation/revisions.txt
@@ -115,7 +115,7 @@ Here's an example to make it more clear:
 ------------------------------
 $ git config push.default current
 $ git config remote.pushdefault myfork
-$ git checkout -b mybranch origin/master
+$ git switch -c mybranch origin/master
 
 $ git rev-parse --symbolic-full-name @{upstream}
 refs/remotes/origin/master
diff --git a/Documentation/user-manual.txt b/Documentation/user-manual.txt
index eff7890274..94799faa2b 100644
--- a/Documentation/user-manual.txt
+++ b/Documentation/user-manual.txt
@@ -122,10 +122,10 @@ Tags are expected to always point at the same version of a project,
 while heads are expected to advance as development progresses.
 
 Create a new branch head pointing to one of these versions and check it
-out using linkgit:git-checkout[1]:
+out using linkgit:git-switch[1]:
 
 ------------------------------------------------
-$ git checkout -b new v2.6.13
+$ git switch -c new v2.6.13
 ------------------------------------------------
 
 The working directory then reflects the contents that the project had
@@ -282,10 +282,10 @@ a summary of the commands:
 	this command will fail with a warning.
 `git branch -D <branch>`::
 	delete the branch `<branch>` irrespective of its merged status.
-`git checkout <branch>`::
+`git switch <branch>`::
 	make the current branch `<branch>`, updating the working
 	directory to reflect the version referenced by `<branch>`.
-`git checkout -b <new> <start-point>`::
+`git switch -c <new> <start-point>`::
 	create a new branch `<new>` referencing `<start-point>`, and
 	check it out.
 
@@ -302,22 +302,22 @@ ref: refs/heads/master
 Examining an old version without creating a new branch
 ------------------------------------------------------
 
-The `git checkout` command normally expects a branch head, but will also
-accept an arbitrary commit; for example, you can check out the commit
-referenced by a tag:
+The `git switch` command normally expects a branch head, but will also
+accept an arbitrary commit when invoked with --detach; for example,
+you can check out the commit referenced by a tag:
 
 ------------------------------------------------
-$ git checkout v2.6.17
+$ git switch --detach v2.6.17
 Note: checking out 'v2.6.17'.
 
 You are in 'detached HEAD' state. You can look around, make experimental
 changes and commit them, and you can discard any commits you make in this
-state without impacting any branches by performing another checkout.
+state without impacting any branches by performing another switch.
 
 If you want to create a new branch to retain commits you create, you may
-do so (now or later) by using -b with the checkout command again. Example:
+do so (now or later) by using -c with the switch command again. Example:
 
-  git checkout -b new_branch_name
+  git switch -c new_branch_name
 
 HEAD is now at 427abfa Linux v2.6.17
 ------------------------------------------------
@@ -373,7 +373,7 @@ You might want to build on one of these remote-tracking branches
 on a branch of your own, just as you would for a tag:
 
 ------------------------------------------------
-$ git checkout -b my-todo-copy origin/todo
+$ git switch -c my-todo-copy origin/todo
 ------------------------------------------------
 
 You can also check out `origin/todo` directly to examine it or
@@ -2211,8 +2211,8 @@ $ git branch --track release origin/master
 These can be easily kept up to date using linkgit:git-pull[1].
 
 -------------------------------------------------
-$ git checkout test && git pull
-$ git checkout release && git pull
+$ git switch test && git pull
+$ git switch release && git pull
 -------------------------------------------------
 
 Important note!  If you have any local changes in these branches, then
@@ -2264,7 +2264,7 @@ tested changes
 2) help future bug hunters that use `git bisect` to find problems
 
 -------------------------------------------------
-$ git checkout -b speed-up-spinlocks v2.6.35
+$ git switch -c speed-up-spinlocks v2.6.35
 -------------------------------------------------
 
 Now you apply the patch(es), run some tests, and commit the change(s).  If
@@ -2279,7 +2279,7 @@ When you are happy with the state of this change, you can merge it into the
 "test" branch in preparation to make it public:
 
 -------------------------------------------------
-$ git checkout test && git merge speed-up-spinlocks
+$ git switch test && git merge speed-up-spinlocks
 -------------------------------------------------
 
 It is unlikely that you would have any conflicts here ... but you might if you
@@ -2291,7 +2291,7 @@ see the value of keeping each patch (or patch series) in its own branch.  It
 means that the patches can be moved into the `release` tree in any order.
 
 -------------------------------------------------
-$ git checkout release && git merge speed-up-spinlocks
+$ git switch release && git merge speed-up-spinlocks
 -------------------------------------------------
 
 After a while, you will have a number of branches, and despite the
@@ -2512,7 +2512,7 @@ Suppose that you create a branch `mywork` on a remote-tracking branch
 `origin`, and create some commits on top of it:
 
 -------------------------------------------------
-$ git checkout -b mywork origin
+$ git switch -c mywork origin
 $ vi file.txt
 $ git commit
 $ vi otherfile.txt
@@ -2552,7 +2552,7 @@ commits without any merges, you may instead choose to use
 linkgit:git-rebase[1]:
 
 -------------------------------------------------
-$ git checkout mywork
+$ git switch mywork
 $ git rebase origin
 -------------------------------------------------
 
@@ -3668,13 +3668,13 @@ change within the submodule, and then update the superproject to reference the
 new commit:
 
 -------------------------------------------------
-$ git checkout master
+$ git switch master
 -------------------------------------------------
 
 or
 
 -------------------------------------------------
-$ git checkout -b fix-up
+$ git switch -c fix-up
 -------------------------------------------------
 
 then
@@ -4194,7 +4194,7 @@ start.
 A good place to start is with the contents of the initial commit, with:
 
 ----------------------------------------------------
-$ git checkout e83c5163
+$ git switch --detach e83c5163
 ----------------------------------------------------
 
 The initial revision lays the foundation for almost everything Git has
@@ -4437,10 +4437,10 @@ Managing branches
 -----------------
 
 -----------------------------------------------
-$ git branch	     # list all local branches in this repo
-$ git checkout test  # switch working directory to branch "test"
-$ git branch new     # create branch "new" starting at current HEAD
-$ git branch -d new  # delete branch "new"
+$ git branch			# list all local branches in this repo
+$ git switch test	        # switch working directory to branch "test"
+$ git branch new		# create branch "new" starting at current HEAD
+$ git branch -d new		# delete branch "new"
 -----------------------------------------------
 
 Instead of basing a new branch on current HEAD (the default), use:
@@ -4456,7 +4456,7 @@ $ git branch new test~10 # ten commits before tip of branch "test"
 Create and switch to a new branch at the same time:
 
 -----------------------------------------------
-$ git checkout -b new v2.6.15
+$ git switch -c new v2.6.15
 -----------------------------------------------
 
 Update and examine branches from the repository you cloned from:
@@ -4467,7 +4467,7 @@ $ git branch -r		# list
   origin/master
   origin/next
   ...
-$ git checkout -b masterwork origin/master
+$ git switch -c masterwork origin/master
 -----------------------------------------------
 
 Fetch a branch from a different repository, and give it a new
diff --git a/advice.c b/advice.c
index 567209aa79..457c1a255e 100644
--- a/advice.c
+++ b/advice.c
@@ -191,13 +191,16 @@ void NORETURN die_conclude_merge(void)
 void detach_advice(const char *new_name)
 {
 	const char *fmt =
-	_("Note: checking out '%s'.\n\n"
+	_("Note: switching to '%s'.\n"
+	"\n"
 	"You are in 'detached HEAD' state. You can look around, make experimental\n"
 	"changes and commit them, and you can discard any commits you make in this\n"
-	"state without impacting any branches by performing another checkout.\n\n"
+	"state without impacting any branches by switching back to a branch.\n"
+	"\n"
 	"If you want to create a new branch to retain commits you create, you may\n"
-	"do so (now or later) by using -b with the checkout command again. Example:\n\n"
-	"  git checkout -b <new-branch-name>\n\n");
+	"do so (now or later) by using -c with the switch command. Example:\n"
+	"\n"
+	"  git switch -c <new-branch-name>\n\n");
 
 	fprintf(stderr, fmt, new_name);
 }
diff --git a/sha1-name.c b/sha1-name.c
index a656481c6a..e5f0832995 100644
--- a/sha1-name.c
+++ b/sha1-name.c
@@ -745,7 +745,7 @@ static int get_oid_basic(const char *str, int len, struct object_id *oid,
 	"because it will be ignored when you just specify 40-hex. These refs\n"
 	"may be created by mistake. For example,\n"
 	"\n"
-	"  git checkout -b $br $(git rev-parse ...)\n"
+	"  git switch -c $br $(git rev-parse ...)\n"
 	"\n"
 	"where \"$br\" is somehow empty and a 40-hex ref is created. Please\n"
 	"examine these refs and maybe delete them. Turn this message off by\n"
diff --git a/t/t2020-checkout-detach.sh b/t/t2020-checkout-detach.sh
index 1fa670625c..f85dbd6740 100755
--- a/t/t2020-checkout-detach.sh
+++ b/t/t2020-checkout-detach.sh
@@ -195,16 +195,16 @@ test_expect_success 'describe_detached_head prints no SHA-1 ellipsis when not as
 
 	# The first detach operation is more chatty than the following ones.
 	cat >1st_detach <<-EOF &&
-	Note: checking out 'HEAD^'.
+	Note: switching to 'HEAD^'.
 
 	You are in 'detached HEAD' state. You can look around, make experimental
 	changes and commit them, and you can discard any commits you make in this
-	state without impacting any branches by performing another checkout.
+	state without impacting any branches by switching back to a branch.
 
 	If you want to create a new branch to retain commits you create, you may
-	do so (now or later) by using -b with the checkout command again. Example:
+	do so (now or later) by using -c with the switch command. Example:
 
-	  git checkout -b <new-branch-name>
+	  git switch -c <new-branch-name>
 
 	HEAD is now at \$commit three
 	EOF
@@ -271,16 +271,16 @@ test_expect_success 'describe_detached_head does print SHA-1 ellipsis when asked
 
 	# The first detach operation is more chatty than the following ones.
 	cat >1st_detach <<-EOF &&
-	Note: checking out 'HEAD^'.
+	Note: switching to 'HEAD^'.
 
 	You are in 'detached HEAD' state. You can look around, make experimental
 	changes and commit them, and you can discard any commits you make in this
-	state without impacting any branches by performing another checkout.
+	state without impacting any branches by switching back to a branch.
 
 	If you want to create a new branch to retain commits you create, you may
-	do so (now or later) by using -b with the checkout command again. Example:
+	do so (now or later) by using -c with the switch command. Example:
 
-	  git checkout -b <new-branch-name>
+	  git switch -c <new-branch-name>
 
 	HEAD is now at \$commit... three
 	EOF

diff --git a/Documentation/git-checkout.txt b/Documentation/git-checkout.txt
index f179b43732..99c8c0dc0f 100644
--- a/Documentation/git-checkout.txt
+++ b/Documentation/git-checkout.txt
@@ -118,7 +118,8 @@ OPTIONS
 --quiet::
 	Quiet, suppress feedback messages.
 
---[no-]progress::
+--progress::
+--no-progress::
 	Progress status is reported on the standard error stream
 	by default when it is attached to a terminal, unless `--quiet`
 	is specified. This flag enables progress reporting even if not
@@ -262,7 +263,7 @@ edits from your current working tree. See the ``Interactive Mode''
 section of linkgit:git-add[1] to learn how to operate the `--patch` mode.
 +
 Note that this option uses the no overlay mode by default (see also
-`--[no-]overlay`), and currently doesn't support overlay mode.
+`--overlay`), and currently doesn't support overlay mode.
 
 --ignore-other-worktrees::
 	`git checkout` refuses when the wanted ref is already checked
@@ -270,7 +271,8 @@ Note that this option uses the no overlay mode by default (see also
 	out anyway. In other words, the ref can be held by more than one
 	worktree.
 
---[no-]recurse-submodules::
+--recurse-submodules::
+--no-recurse-submodules::
 	Using --recurse-submodules will update the content of all initialized
 	submodules according to the commit recorded in the superproject. If
 	local modifications in a submodule would be overwritten the checkout
@@ -283,7 +285,8 @@ Note that this option uses the no overlay mode by default (see also
 	Do not attempt to create a branch if a remote tracking branch
 	of the same name exists.
 
---[no-]overlay::
+--overlay::
+--no-overlay::
 	In the default overlay mode, `git checkout` never
 	removes files from the index or the working tree.  When
 	specifying `--no-overlay`, files that appear in the index and

diff --git a/Documentation/git-checkout.txt b/Documentation/git-checkout.txt
index 99c8c0dc0f..28817cfa41 100644
--- a/Documentation/git-checkout.txt
+++ b/Documentation/git-checkout.txt
@@ -23,7 +23,7 @@ or the specified tree.  If no paths are given, 'git checkout' will
 also update `HEAD` to set the specified branch as the current
 branch.
 
-'git checkout' <branch>::
+'git checkout' [<branch>]::
 	To prepare for working on <branch>, switch to it by updating
 	the index and the files in the working tree, and by pointing
 	HEAD at the branch. Local modifications to the files in the

Documentation/git-checkout.txt, Documentation/git-merge.txt

diff --git a/Documentation/git-checkout.txt b/Documentation/git-checkout.txt
index 28817cfa41..5280d1f9ed 100644
--- a/Documentation/git-checkout.txt
+++ b/Documentation/git-checkout.txt
@@ -271,6 +271,12 @@ Note that this option uses the no overlay mode by default (see also
 	out anyway. In other words, the ref can be held by more than one
 	worktree.
 
+--overwrite-ignore::
+--no-overwrite-ignore::
+	Silently overwrite ignored files when switching branches. This
+	is the default behavior. Use `--no-overwrite-ignore` to abort
+	the operation when the new branch contains ignored files.
+
 --recurse-submodules::
 --no-recurse-submodules::
 	Using --recurse-submodules will update the content of all initialized
diff --git a/Documentation/git-merge.txt b/Documentation/git-merge.txt
index 4cc86469f3..6a9163d8fe 100644
--- a/Documentation/git-merge.txt
+++ b/Documentation/git-merge.txt
@@ -87,6 +87,11 @@ will be appended to the specified message.
 	Allow the rerere mechanism to update the index with the
 	result of auto-conflict resolution if possible.
 
+--overwrite-ignore::
+--no-overwrite-ignore::
+	Silently overwrite ignored files from the merge result. This
+	is the default behavior. Use `--no-overwrite-ignore` to abort.
+
 --abort::
 	Abort the current conflict resolution process, and
 	try to reconstruct the pre-merge state.

diff --git a/Documentation/git-checkout.txt b/Documentation/git-checkout.txt
index 5280d1f9ed..1b9d689933 100644
--- a/Documentation/git-checkout.txt
+++ b/Documentation/git-checkout.txt
@@ -24,14 +24,14 @@ also update `HEAD` to set the specified branch as the current
 branch.
 
 'git checkout' [<branch>]::
-	To prepare for working on <branch>, switch to it by updating
+	To prepare for working on `<branch>`, switch to it by updating
 	the index and the files in the working tree, and by pointing
 	HEAD at the branch. Local modifications to the files in the
 	working tree are kept, so that they can be committed to the
-	<branch>.
+	`<branch>`.
 +
-If <branch> is not found but there does exist a tracking branch in
-exactly one remote (call it <remote>) with a matching name, treat as
+If `<branch>` is not found but there does exist a tracking branch in
+exactly one remote (call it `<remote>`) with a matching name, treat as
 equivalent to
 +
 ------------
@@ -47,7 +47,7 @@ branches from there if `<branch>` is ambiguous but exists on the
 'origin' remote. See also `checkout.defaultRemote` in
 linkgit:git-config[1].
 +
-You could omit <branch>, in which case the command degenerates to
+You could omit `<branch>`, in which case the command degenerates to
 "check out the current branch", which is a glorified no-op with
 rather expensive side-effects to show only the tracking information,
 if exists, for the current branch.
@@ -61,7 +61,7 @@ if exists, for the current branch.
 	`--track` without `-b` implies branch creation; see the
 	description of `--track` below.
 +
-If `-B` is given, <new_branch> is created if it doesn't exist; otherwise, it
+If `-B` is given, `<new_branch>` is created if it doesn't exist; otherwise, it
 is reset. This is the transactional equivalent of
 +
 ------------
@@ -75,25 +75,25 @@ successful.
 'git checkout' --detach [<branch>]::
 'git checkout' [--detach] <commit>::
 
-	Prepare to work on top of <commit>, by detaching HEAD at it
+	Prepare to work on top of `<commit>`, by detaching HEAD at it
 	(see "DETACHED HEAD" section), and updating the index and the
 	files in the working tree.  Local modifications to the files
 	in the working tree are kept, so that the resulting working
 	tree will be the state recorded in the commit plus the local
 	modifications.
 +
-When the <commit> argument is a branch name, the `--detach` option can
+When the `<commit>` argument is a branch name, the `--detach` option can
 be used to detach HEAD at the tip of the branch (`git checkout
-<branch>` would check out that branch without detaching HEAD).
+`<branch>`` would check out that branch without detaching HEAD).
 +
-Omitting <branch> detaches HEAD at the tip of the current branch.
+Omitting `<branch>` detaches HEAD at the tip of the current branch.
 
 'git checkout' [<tree-ish>] [--] <pathspec>...::
 
 	Overwrite paths in the working tree by replacing with the
-	contents in the index or in the <tree-ish> (most often a
-	commit).  When a <tree-ish> is given, the paths that
-	match the <pathspec> are updated both in the index and in
+	contents in the index or in the `<tree-ish>` (most often a
+	commit).  When a `<tree-ish>` is given, the paths that
+	match the `<pathspec>` are updated both in the index and in
 	the working tree.
 +
 The index may contain unmerged entries because of a previous failed merge.
@@ -155,12 +155,12 @@ on your side branch as `theirs` (i.e. "one contributor's work on top
 of it").
 
 -b <new_branch>::
-	Create a new branch named <new_branch> and start it at
-	<start_point>; see linkgit:git-branch[1] for details.
+	Create a new branch named `<new_branch>` and start it at
+	`<start_point>`; see linkgit:git-branch[1] for details.
 
 -B <new_branch>::
-	Creates the branch <new_branch> and start it at <start_point>;
-	if it already exists, then reset it to <start_point>. This is
+	Creates the branch `<new_branch>` and start it at `<start_point>`;
+	if it already exists, then reset it to `<start_point>`. This is
 	equivalent to running "git branch" with "-f"; see
 	linkgit:git-branch[1] for details.
 
@@ -191,19 +191,19 @@ explicitly give a name with `-b` in such a case.
 	Rather than checking out a branch to work on it, check out a
 	commit for inspection and discardable experiments.
 	This is the default behavior of "git checkout <commit>" when
-	<commit> is not a branch name.  See the "DETACHED HEAD" section
+	`<commit>` is not a branch name.  See the "DETACHED HEAD" section
 	below for details.
 
 --orphan <new_branch>::
-	Create a new 'orphan' branch, named <new_branch>, started from
-	<start_point> and switch to it.  The first commit made on this
+	Create a new 'orphan' branch, named `<new_branch>`, started from
+	`<start_point>` and switch to it.  The first commit made on this
 	new branch will have no parents and it will be the root of a new
 	history totally disconnected from all the other branches and
 	commits.
 +
 The index and the working tree are adjusted as if you had previously run
 "git checkout <start_point>".  This allows you to start a new history
-that records a set of paths similar to <start_point> by easily running
+that records a set of paths similar to `<start_point>` by easily running
 "git commit -a" to make the root commit.
 +
 This can be useful when you want to publish the tree from a commit
@@ -213,7 +213,7 @@ whose full history contains proprietary or otherwise encumbered bits of
 code.
 +
 If you want to start a disconnected history that records a set of paths
-that is totally different from the one of <start_point>, then you should
+that is totally different from the one of `<start_point>`, then you should
 clear the index and the working tree right after creating the orphan
 branch by running "git rm -rf ." from the top level of the working tree.
 Afterwards you will be ready to prepare your new files, repopulating the
@@ -221,9 +221,9 @@ working tree, by copying them from elsewhere, extracting a tarball, etc.
 
 --ignore-skip-worktree-bits::
 	In sparse checkout mode, `git checkout -- <paths>` would
-	update only entries matched by <paths> and sparse patterns
+	update only entries matched by `<paths>` and sparse patterns
 	in $GIT_DIR/info/sparse-checkout. This option ignores
-	the sparse patterns and adds back any files in <paths>.
+	the sparse patterns and adds back any files in `<paths>`.
 
 -m::
 --merge::
@@ -254,9 +254,9 @@ the conflicted merge in the specified paths.
 -p::
 --patch::
 	Interactively select hunks in the difference between the
-	<tree-ish> (or the index, if unspecified) and the working
+	`<tree-ish>` (or the index, if unspecified) and the working
 	tree.  The chosen hunks are then applied in reverse to the
-	working tree (and if a <tree-ish> was specified, the index).
+	working tree (and if a `<tree-ish>` was specified, the index).
 +
 This means that you can use `git checkout -p` to selectively discard
 edits from your current working tree. See the ``Interactive Mode''
@@ -279,10 +279,10 @@ Note that this option uses the no overlay mode by default (see also
 
 --recurse-submodules::
 --no-recurse-submodules::
-	Using --recurse-submodules will update the content of all initialized
+	Using `--recurse-submodules` will update the content of all initialized
 	submodules according to the commit recorded in the superproject. If
 	local modifications in a submodule would be overwritten the checkout
-	will fail unless `-f` is used. If nothing (or --no-recurse-submodules)
+	will fail unless `-f` is used. If nothing (or `--no-recurse-submodules`)
 	is used, the work trees of submodules will not be updated.
 	Just like linkgit:git-submodule[1], this will detach the
 	submodules HEAD.
@@ -296,8 +296,8 @@ Note that this option uses the no overlay mode by default (see also
 	In the default overlay mode, `git checkout` never
 	removes files from the index or the working tree.  When
 	specifying `--no-overlay`, files that appear in the index and
-	working tree, but not in <tree-ish> are removed, to make them
-	match <tree-ish> exactly.
+	working tree, but not in `<tree-ish>` are removed, to make them
+	match `<tree-ish>` exactly.
 
 <branch>::
 	Branch to checkout; if it refers to a branch (i.e., a name that,

diff --git a/Documentation/git-checkout.txt b/Documentation/git-checkout.txt
index 1b9d689933..af5906fbf5 100644
--- a/Documentation/git-checkout.txt
+++ b/Documentation/git-checkout.txt
@@ -26,7 +26,7 @@ branch.
 'git checkout' [<branch>]::
 	To prepare for working on `<branch>`, switch to it by updating
 	the index and the files in the working tree, and by pointing
-	HEAD at the branch. Local modifications to the files in the
+	`HEAD` at the branch. Local modifications to the files in the
 	working tree are kept, so that they can be committed to the
 	`<branch>`.
 +
@@ -75,7 +75,7 @@ successful.
 'git checkout' --detach [<branch>]::
 'git checkout' [--detach] <commit>::
 
-	Prepare to work on top of `<commit>`, by detaching HEAD at it
+	Prepare to work on top of `<commit>`, by detaching `HEAD` at it
 	(see "DETACHED HEAD" section), and updating the index and the
 	files in the working tree.  Local modifications to the files
 	in the working tree are kept, so that the resulting working
@@ -83,10 +83,10 @@ successful.
 	modifications.
 +
 When the `<commit>` argument is a branch name, the `--detach` option can
-be used to detach HEAD at the tip of the branch (`git checkout
-`<branch>`` would check out that branch without detaching HEAD).
+be used to detach `HEAD` at the tip of the branch (`git checkout
+<branch>` would check out that branch without detaching `HEAD`).
 +
-Omitting `<branch>` detaches HEAD at the tip of the current branch.
+Omitting `<branch>` detaches `HEAD` at the tip of the current branch.
 
 'git checkout' [<tree-ish>] [--] <pathspec>...::
 
@@ -128,7 +128,7 @@ OPTIONS
 -f::
 --force::
 	When switching branches, proceed even if the index or the
-	working tree differs from HEAD.  This is used to throw away
+	working tree differs from `HEAD`.  This is used to throw away
 	local changes.
 +
 When checking out paths from the index, do not fail upon unmerged
@@ -173,15 +173,15 @@ If no `-b` option is given, the name of the new branch will be
 derived from the remote-tracking branch, by looking at the local part of
 the refspec configured for the corresponding remote, and then stripping
 the initial part up to the "*".
-This would tell us to use "hack" as the local branch when branching
-off of "origin/hack" (or "remotes/origin/hack", or even
-"refs/remotes/origin/hack").  If the given name has no slash, or the above
+This would tell us to use `hack` as the local branch when branching
+off of `origin/hack` (or `remotes/origin/hack`, or even
+`refs/remotes/origin/hack`).  If the given name has no slash, or the above
 guessing results in an empty name, the guessing is aborted.  You can
 explicitly give a name with `-b` in such a case.
 
 --no-track::
 	Do not set up "upstream" configuration, even if the
-	branch.autoSetupMerge configuration variable is true.
+	`branch.autoSetupMerge` configuration variable is true.
 
 -l::
 	Create the new branch's reflog; see linkgit:git-branch[1] for
@@ -190,7 +190,7 @@ explicitly give a name with `-b` in such a case.
 --detach::
 	Rather than checking out a branch to work on it, check out a
 	commit for inspection and discardable experiments.
-	This is the default behavior of "git checkout <commit>" when
+	This is the default behavior of `git checkout <commit>` when
 	`<commit>` is not a branch name.  See the "DETACHED HEAD" section
 	below for details.
 
@@ -202,9 +202,9 @@ explicitly give a name with `-b` in such a case.
 	commits.
 +
 The index and the working tree are adjusted as if you had previously run
-"git checkout <start_point>".  This allows you to start a new history
+`git checkout <start_point>`.  This allows you to start a new history
 that records a set of paths similar to `<start_point>` by easily running
-"git commit -a" to make the root commit.
+`git commit -a` to make the root commit.
 +
 This can be useful when you want to publish the tree from a commit
 without exposing its full history. You might want to do this to publish
@@ -215,14 +215,14 @@ code.
 If you want to start a disconnected history that records a set of paths
 that is totally different from the one of `<start_point>`, then you should
 clear the index and the working tree right after creating the orphan
-branch by running "git rm -rf ." from the top level of the working tree.
+branch by running `git rm -rf .` from the top level of the working tree.
 Afterwards you will be ready to prepare your new files, repopulating the
 working tree, by copying them from elsewhere, extracting a tarball, etc.
 
 --ignore-skip-worktree-bits::
 	In sparse checkout mode, `git checkout -- <paths>` would
 	update only entries matched by `<paths>` and sparse patterns
-	in $GIT_DIR/info/sparse-checkout. This option ignores
+	in `$GIT_DIR/info/sparse-checkout`. This option ignores
 	the sparse patterns and adds back any files in `<paths>`.
 
 -m::
@@ -245,9 +245,9 @@ When checking out paths from the index, this option lets you recreate
 the conflicted merge in the specified paths.
 
 --conflict=<style>::
-	The same as --merge option above, but changes the way the
+	The same as `--merge` option above, but changes the way the
 	conflicting hunks are presented, overriding the
-	merge.conflictStyle configuration variable.  Possible values are
+	`merge.conflictStyle` configuration variable.  Possible values are
 	"merge" (default) and "diff3" (in addition to what is shown by
 	"merge" style, shows the original contents).
 
@@ -285,7 +285,7 @@ Note that this option uses the no overlay mode by default (see also
 	will fail unless `-f` is used. If nothing (or `--no-recurse-submodules`)
 	is used, the work trees of submodules will not be updated.
 	Just like linkgit:git-submodule[1], this will detach the
-	submodules HEAD.
+	submodules' `HEAD`.
 
 --no-guess::
 	Do not attempt to create a branch if a remote tracking branch
@@ -303,14 +303,14 @@ Note that this option uses the no overlay mode by default (see also
 	Branch to checkout; if it refers to a branch (i.e., a name that,
 	when prepended with "refs/heads/", is a valid ref), then that
 	branch is checked out. Otherwise, if it refers to a valid
-	commit, your HEAD becomes "detached" and you are no longer on
+	commit, your `HEAD` becomes "detached" and you are no longer on
 	any branch (see below for details).
 +
-You can use the `"@{-N}"` syntax to refer to the N-th last
+You can use the `@{-N}` syntax to refer to the N-th last
 branch/commit checked out using "git checkout" operation. You may
-also specify `-` which is synonymous to `"@{-1}"`.
+also specify `-` which is synonymous to `@{-1}`.
 +
-As a special case, you may use `"A...B"` as a shortcut for the
+As a special case, you may use `A...B` as a shortcut for the
 merge base of `A` and `B` if there is exactly one merge base. You can
 leave out at most one of `A` and `B`, in which case it defaults to `HEAD`.
 
@@ -319,7 +319,7 @@ leave out at most one of `A` and `B`, in which case it defaults to `HEAD`.
 
 <start_point>::
 	The name of a commit at which to start the new branch; see
-	linkgit:git-branch[1] for details. Defaults to HEAD.
+	linkgit:git-branch[1] for details. Defaults to `HEAD`.
 
 <tree-ish>::
 	Tree to checkout from (when paths are given). If not specified,
@@ -329,9 +329,9 @@ leave out at most one of `A` and `B`, in which case it defaults to `HEAD`.
 
 DETACHED HEAD
 -------------
-HEAD normally refers to a named branch (e.g. 'master'). Meanwhile, each
+`HEAD` normally refers to a named branch (e.g. `master`). Meanwhile, each
 branch refers to a specific commit. Let's look at a repo with three
-commits, one of them tagged, and with branch 'master' checked out:
+commits, one of them tagged, and with branch `master` checked out:
 
 ------------
            HEAD (refers to branch 'master')
@@ -344,10 +344,10 @@ a---b---c  branch 'master' (refers to commit 'c')
 ------------
 
 When a commit is created in this state, the branch is updated to refer to
-the new commit. Specifically, 'git commit' creates a new commit 'd', whose
-parent is commit 'c', and then updates branch 'master' to refer to new
-commit 'd'. HEAD still refers to branch 'master' and so indirectly now refers
-to commit 'd':
+the new commit. Specifically, 'git commit' creates a new commit `d`, whose
+parent is commit `c`, and then updates branch `master` to refer to new
+commit `d`. `HEAD` still refers to branch `master` and so indirectly now refers
+to commit `d`:
 
 ------------
 $ edit; git add; git commit
@@ -364,7 +364,7 @@ a---b---c---d  branch 'master' (refers to commit 'd')
 It is sometimes useful to be able to checkout a commit that is not at
 the tip of any named branch, or even to create a new commit that is not
 referenced by a named branch. Let's look at what happens when we
-checkout commit 'b' (here we show two ways this may be done):
+checkout commit `b` (here we show two ways this may be done):
 
 ------------
 $ git checkout v2.0  # or
@@ -379,9 +379,9 @@ a---b---c---d  branch 'master' (refers to commit 'd')
   tag 'v2.0' (refers to commit 'b')
 ------------
 
-Notice that regardless of which checkout command we use, HEAD now refers
-directly to commit 'b'. This is known as being in detached HEAD state.
-It means simply that HEAD refers to a specific commit, as opposed to
+Notice that regardless of which checkout command we use, `HEAD` now refers
+directly to commit `b`. This is known as being in detached `HEAD` state.
+It means simply that `HEAD` refers to a specific commit, as opposed to
 referring to a named branch. Let's see what happens when we create a commit:
 
 ------------
@@ -398,7 +398,7 @@ a---b---c---d  branch 'master' (refers to commit 'd')
   tag 'v2.0' (refers to commit 'b')
 ------------
 
-There is now a new commit 'e', but it is referenced only by HEAD. We can
+There is now a new commit `e`, but it is referenced only by `HEAD`. We can
 of course add yet another commit in this state:
 
 ------------
@@ -416,7 +416,7 @@ a---b---c---d  branch 'master' (refers to commit 'd')
 ------------
 
 In fact, we can perform all the normal Git operations. But, let's look
-at what happens when we then checkout master:
+at what happens when we then checkout `master`:
 
 ------------
 $ git checkout master
@@ -431,9 +431,9 @@ a---b---c---d  branch 'master' (refers to commit 'd')
 ------------
 
 It is important to realize that at this point nothing refers to commit
-'f'. Eventually commit 'f' (and by extension commit 'e') will be deleted
+`f`. Eventually commit `f` (and by extension commit `e`) will be deleted
 by the routine Git garbage collection process, unless we create a reference
-before that happens. If we have not yet moved away from commit 'f',
+before that happens. If we have not yet moved away from commit `f`,
 any of these will create a reference to it:
 
 ------------
@@ -442,19 +442,19 @@ $ git branch foo        <2>
 $ git tag foo           <3>
 ------------
 
-<1> creates a new branch 'foo', which refers to commit 'f', and then
-    updates HEAD to refer to branch 'foo'. In other words, we'll no longer
-    be in detached HEAD state after this command.
+<1> creates a new branch `foo`, which refers to commit `f`, and then
+    updates `HEAD` to refer to branch `foo`. In other words, we'll no longer
+    be in detached `HEAD` state after this command.
 
-<2> similarly creates a new branch 'foo', which refers to commit 'f',
-    but leaves HEAD detached.
+<2> similarly creates a new branch `foo`, which refers to commit `f`,
+    but leaves `HEAD` detached.
 
-<3> creates a new tag 'foo', which refers to commit 'f',
-    leaving HEAD detached.
+<3> creates a new tag `foo`, which refers to commit `f`,
+    leaving `HEAD` detached.
 
-If we have moved away from commit 'f', then we must first recover its object
+If we have moved away from commit `f`, then we must first recover its object
 name (typically by using git reflog), and then we can create a reference to
-it. For example, to see the last two commits to which HEAD referred, we
+it. For example, to see the last two commits to which `HEAD` referred, we
 can use either of these commands:
 
 ------------
@@ -465,12 +465,12 @@ $ git log -g -2 HEAD
 ARGUMENT DISAMBIGUATION
 -----------------------
 
-When there is only one argument given and it is not `--` (e.g. "git
-checkout abc"), and when the argument is both a valid `<tree-ish>`
-(e.g. a branch "abc" exists) and a valid `<pathspec>` (e.g. a file
+When there is only one argument given and it is not `--` (e.g. `git
+checkout abc`), and when the argument is both a valid `<tree-ish>`
+(e.g. a branch `abc` exists) and a valid `<pathspec>` (e.g. a file
 or a directory whose name is "abc" exists), Git would usually ask
 you to disambiguate.  Because checking out a branch is so common an
-operation, however, "git checkout abc" takes "abc" as a `<tree-ish>`
+operation, however, `git checkout abc` takes "abc" as a `<tree-ish>`
 in such a situation.  Use `git checkout -- <pathspec>` if you want
 to checkout these paths out of the index.
 
@@ -478,7 +478,7 @@ EXAMPLES
 --------
 
 . The following sequence checks out the `master` branch, reverts
-  the `Makefile` to two revisions back, deletes hello.c by
+  the `Makefile` to two revisions back, deletes `hello.c` by
   mistake, and gets it back from the index.
 +
 ------------
@@ -490,7 +490,7 @@ $ git checkout hello.c            <3>
 +
 <1> switch branch
 <2> take a file out of another commit
-<3> restore hello.c from the index
+<3> restore `hello.c` from the index
 +
 If you want to check out _all_ C source files out of the index,
 you can say
@@ -519,7 +519,7 @@ $ git checkout -- hello.c
 $ git checkout mytopic
 ------------
 +
-However, your "wrong" branch and correct "mytopic" branch may
+However, your "wrong" branch and correct `mytopic` branch may
 differ in files that you have modified locally, in which case
 the above checkout would fail like this:
 +

diff --git a/t/t2014-switch.sh b/t/t2014-checkout-switch.sh
similarity index 100%
rename from t/t2014-switch.sh
rename to t/t2014-checkout-switch.sh

diff --git a/builtin/checkout.c b/builtin/checkout.c
index 0e6037b296..cbdcb1417f 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -1081,6 +1081,34 @@ static int git_checkout_config(const char *var, const char *value, void *cb)
 	return git_xmerge_config(var, value, NULL);
 }
 
+static void setup_new_branch_info_and_source_tree(
+	struct branch_info *new_branch_info,
+	struct checkout_opts *opts,
+	struct object_id *rev,
+	const char *arg)
+{
+	struct tree **source_tree = &opts->source_tree;
+	struct object_id branch_rev;
+
+	new_branch_info->name = arg;
+	setup_branch_path(new_branch_info);
+
+	if (!check_refname_format(new_branch_info->path, 0) &&
+	    !read_ref(new_branch_info->path, &branch_rev))
+		oidcpy(rev, &branch_rev);
+	else
+		new_branch_info->path = NULL; /* not an existing branch */
+
+	new_branch_info->commit = lookup_commit_reference_gently(the_repository, rev, 1);
+	if (!new_branch_info->commit) {
+		/* not a commit */
+		*source_tree = parse_tree_indirect(rev);
+	} else {
+		parse_commit_or_die(new_branch_info->commit);
+		*source_tree = get_commit_tree(new_branch_info->commit);
+	}
+}
+
 static int parse_branchname_arg(int argc, const char **argv,
 				int dwim_new_local_branch_ok,
 				struct branch_info *new_branch_info,
@@ -1088,10 +1116,8 @@ static int parse_branchname_arg(int argc, const char **argv,
 				struct object_id *rev,
 				int *dwim_remotes_matched)
 {
-	struct tree **source_tree = &opts->source_tree;
 	const char **new_branch = &opts->new_branch;
 	int argcount = 0;
-	struct object_id branch_rev;
 	const char *arg;
 	int dash_dash_pos;
 	int has_dash_dash = 0;
@@ -1213,26 +1239,11 @@ static int parse_branchname_arg(int argc, const char **argv,
 	argv++;
 	argc--;
 
-	new_branch_info->name = arg;
-	setup_branch_path(new_branch_info);
-
-	if (!check_refname_format(new_branch_info->path, 0) &&
-	    !read_ref(new_branch_info->path, &branch_rev))
-		oidcpy(rev, &branch_rev);
-	else
-		new_branch_info->path = NULL; /* not an existing branch */
+	setup_new_branch_info_and_source_tree(new_branch_info, opts, rev, arg);
 
-	new_branch_info->commit = lookup_commit_reference_gently(the_repository, rev, 1);
-	if (!new_branch_info->commit) {
-		/* not a commit */
-		*source_tree = parse_tree_indirect(rev);
-	} else {
-		parse_commit_or_die(new_branch_info->commit);
-		*source_tree = get_commit_tree(new_branch_info->commit);
-	}
-
-	if (!*source_tree)                   /* case (1): want a tree */
+	if (!opts->source_tree)                   /* case (1): want a tree */
 		die(_("reference is not a tree: %s"), arg);
+
 	if (!has_dash_dash) {	/* case (3).(d) -> (1) */
 		/*
 		 * Do not complain the most common case

diff --git a/builtin/checkout.c b/builtin/checkout.c
index cbdcb1417f..baefe3c942 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -1341,82 +1341,83 @@ static int checkout_branch(struct checkout_opts *opts,
 
 int cmd_checkout(int argc, const char **argv, const char *prefix)
 {
-	struct checkout_opts opts;
+	struct checkout_opts real_opts;
+	struct checkout_opts *opts = &real_opts;
 	struct branch_info new_branch_info;
 	char *conflict_style = NULL;
 	int dwim_new_local_branch, no_dwim_new_local_branch = 0;
 	int dwim_remotes_matched = 0;
 	struct option options[] = {
-		OPT__QUIET(&opts.quiet, N_("suppress progress reporting")),
-		OPT_STRING('b', NULL, &opts.new_branch, N_("branch"),
+		OPT__QUIET(&opts->quiet, N_("suppress progress reporting")),
+		OPT_STRING('b', NULL, &opts->new_branch, N_("branch"),
 			   N_("create and checkout a new branch")),
-		OPT_STRING('B', NULL, &opts.new_branch_force, N_("branch"),
+		OPT_STRING('B', NULL, &opts->new_branch_force, N_("branch"),
 			   N_("create/reset and checkout a branch")),
-		OPT_BOOL('l', NULL, &opts.new_branch_log, N_("create reflog for new branch")),
-		OPT_BOOL(0, "detach", &opts.force_detach, N_("detach HEAD at named commit")),
-		OPT_SET_INT('t', "track",  &opts.track, N_("set upstream info for new branch"),
+		OPT_BOOL('l', NULL, &opts->new_branch_log, N_("create reflog for new branch")),
+		OPT_BOOL(0, "detach", &opts->force_detach, N_("detach HEAD at named commit")),
+		OPT_SET_INT('t', "track",  &opts->track, N_("set upstream info for new branch"),
 			BRANCH_TRACK_EXPLICIT),
-		OPT_STRING(0, "orphan", &opts.new_orphan_branch, N_("new-branch"), N_("new unparented branch")),
-		OPT_SET_INT_F('2', "ours", &opts.writeout_stage,
+		OPT_STRING(0, "orphan", &opts->new_orphan_branch, N_("new-branch"), N_("new unparented branch")),
+		OPT_SET_INT_F('2', "ours", &opts->writeout_stage,
 			      N_("checkout our version for unmerged files"),
 			      2, PARSE_OPT_NONEG),
-		OPT_SET_INT_F('3', "theirs", &opts.writeout_stage,
+		OPT_SET_INT_F('3', "theirs", &opts->writeout_stage,
 			      N_("checkout their version for unmerged files"),
 			      3, PARSE_OPT_NONEG),
-		OPT__FORCE(&opts.force, N_("force checkout (throw away local modifications)"),
+		OPT__FORCE(&opts->force, N_("force checkout (throw away local modifications)"),
 			   PARSE_OPT_NOCOMPLETE),
-		OPT_BOOL('m', "merge", &opts.merge, N_("perform a 3-way merge with the new branch")),
-		OPT_BOOL_F(0, "overwrite-ignore", &opts.overwrite_ignore,
+		OPT_BOOL('m', "merge", &opts->merge, N_("perform a 3-way merge with the new branch")),
+		OPT_BOOL_F(0, "overwrite-ignore", &opts->overwrite_ignore,
 			   N_("update ignored files (default)"),
 			   PARSE_OPT_NOCOMPLETE),
 		OPT_STRING(0, "conflict", &conflict_style, N_("style"),
 			   N_("conflict style (merge or diff3)")),
-		OPT_BOOL('p', "patch", &opts.patch_mode, N_("select hunks interactively")),
-		OPT_BOOL(0, "ignore-skip-worktree-bits", &opts.ignore_skipworktree,
+		OPT_BOOL('p', "patch", &opts->patch_mode, N_("select hunks interactively")),
+		OPT_BOOL(0, "ignore-skip-worktree-bits", &opts->ignore_skipworktree,
 			 N_("do not limit pathspecs to sparse entries only")),
 		OPT_BOOL(0, "no-guess", &no_dwim_new_local_branch,
 			 N_("do not second guess 'git checkout <no-such-branch>'")),
-		OPT_BOOL(0, "ignore-other-worktrees", &opts.ignore_other_worktrees,
+		OPT_BOOL(0, "ignore-other-worktrees", &opts->ignore_other_worktrees,
 			 N_("do not check if another worktree is holding the given ref")),
 		{ OPTION_CALLBACK, 0, "recurse-submodules", NULL,
 			    "checkout", "control recursive updating of submodules",
 			    PARSE_OPT_OPTARG, option_parse_recurse_submodules_worktree_updater },
-		OPT_BOOL(0, "progress", &opts.show_progress, N_("force progress reporting")),
-		OPT_BOOL(0, "overlay", &opts.overlay_mode, N_("use overlay mode (default)")),
+		OPT_BOOL(0, "progress", &opts->show_progress, N_("force progress reporting")),
+		OPT_BOOL(0, "overlay", &opts->overlay_mode, N_("use overlay mode (default)")),
 		OPT_END(),
 	};
 
-	memset(&opts, 0, sizeof(opts));
+	memset(opts, 0, sizeof(*opts));
 	memset(&new_branch_info, 0, sizeof(new_branch_info));
-	opts.overwrite_ignore = 1;
-	opts.prefix = prefix;
-	opts.show_progress = -1;
-	opts.overlay_mode = -1;
+	opts->overwrite_ignore = 1;
+	opts->prefix = prefix;
+	opts->show_progress = -1;
+	opts->overlay_mode = -1;
 
-	git_config(git_checkout_config, &opts);
+	git_config(git_checkout_config, opts);
 
-	opts.track = BRANCH_TRACK_UNSPECIFIED;
+	opts->track = BRANCH_TRACK_UNSPECIFIED;
 
 	argc = parse_options(argc, argv, prefix, options, checkout_usage,
 			     PARSE_OPT_KEEP_DASHDASH);
 
 	dwim_new_local_branch = !no_dwim_new_local_branch;
-	if (opts.show_progress < 0) {
-		if (opts.quiet)
-			opts.show_progress = 0;
+	if (opts->show_progress < 0) {
+		if (opts->quiet)
+			opts->show_progress = 0;
 		else
-			opts.show_progress = isatty(2);
+			opts->show_progress = isatty(2);
 	}
 
 	if (conflict_style) {
-		opts.merge = 1; /* implied */
+		opts->merge = 1; /* implied */
 		git_xmerge_config("merge.conflictstyle", conflict_style, NULL);
 	}
 
-	if ((!!opts.new_branch + !!opts.new_branch_force + !!opts.new_orphan_branch) > 1)
+	if ((!!opts->new_branch + !!opts->new_branch_force + !!opts->new_orphan_branch) > 1)
 		die(_("-b, -B and --orphan are mutually exclusive"));
 
-	if (opts.overlay_mode == 1 && opts.patch_mode)
+	if (opts->overlay_mode == 1 && opts->patch_mode)
 		die(_("-p and --overlay are mutually exclusive"));
 
 	/*
@@ -1424,14 +1425,14 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 	 * and new_branch_force and new_orphan_branch will tell us which one of
 	 * -b/-B/--orphan is being used.
 	 */
-	if (opts.new_branch_force)
-		opts.new_branch = opts.new_branch_force;
+	if (opts->new_branch_force)
+		opts->new_branch = opts->new_branch_force;
 
-	if (opts.new_orphan_branch)
-		opts.new_branch = opts.new_orphan_branch;
+	if (opts->new_orphan_branch)
+		opts->new_branch = opts->new_orphan_branch;
 
 	/* --track without -b/-B/--orphan should DWIM */
-	if (opts.track != BRANCH_TRACK_UNSPECIFIED && !opts.new_branch) {
+	if (opts->track != BRANCH_TRACK_UNSPECIFIED && !opts->new_branch) {
 		const char *argv0 = argv[0];
 		if (!argc || !strcmp(argv0, "--"))
 			die(_("--track needs a branch name"));
@@ -1440,7 +1441,7 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 		argv0 = strchr(argv0, '/');
 		if (!argv0 || !argv0[1])
 			die(_("missing branch name; try -b"));
-		opts.new_branch = argv0 + 1;
+		opts->new_branch = argv0 + 1;
 	}
 
 	/*
@@ -1459,56 +1460,56 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 	if (argc) {
 		struct object_id rev;
 		int dwim_ok =
-			!opts.patch_mode &&
+			!opts->patch_mode &&
 			dwim_new_local_branch &&
-			opts.track == BRANCH_TRACK_UNSPECIFIED &&
-			!opts.new_branch;
+			opts->track == BRANCH_TRACK_UNSPECIFIED &&
+			!opts->new_branch;
 		int n = parse_branchname_arg(argc, argv, dwim_ok,
-					     &new_branch_info, &opts, &rev,
+					     &new_branch_info, opts, &rev,
 					     &dwim_remotes_matched);
 		argv += n;
 		argc -= n;
 	}
 
 	if (argc) {
-		parse_pathspec(&opts.pathspec, 0,
-			       opts.patch_mode ? PATHSPEC_PREFIX_ORIGIN : 0,
+		parse_pathspec(&opts->pathspec, 0,
+			       opts->patch_mode ? PATHSPEC_PREFIX_ORIGIN : 0,
 			       prefix, argv);
 
-		if (!opts.pathspec.nr)
+		if (!opts->pathspec.nr)
 			die(_("invalid path specification"));
 
 		/*
 		 * Try to give more helpful suggestion.
 		 * new_branch && argc > 1 will be caught later.
 		 */
-		if (opts.new_branch && argc == 1)
+		if (opts->new_branch && argc == 1)
 			die(_("'%s' is not a commit and a branch '%s' cannot be created from it"),
-				argv[0], opts.new_branch);
+				argv[0], opts->new_branch);
 
-		if (opts.force_detach)
+		if (opts->force_detach)
 			die(_("git checkout: --detach does not take a path argument '%s'"),
 			    argv[0]);
 
-		if (1 < !!opts.writeout_stage + !!opts.force + !!opts.merge)
+		if (1 < !!opts->writeout_stage + !!opts->force + !!opts->merge)
 			die(_("git checkout: --ours/--theirs, --force and --merge are incompatible when\n"
 			      "checking out of the index."));
 	}
 
-	if (opts.new_branch) {
+	if (opts->new_branch) {
 		struct strbuf buf = STRBUF_INIT;
 
-		if (opts.new_branch_force)
-			opts.branch_exists = validate_branchname(opts.new_branch, &buf);
+		if (opts->new_branch_force)
+			opts->branch_exists = validate_branchname(opts->new_branch, &buf);
 		else
-			opts.branch_exists =
-				validate_new_branchname(opts.new_branch, &buf, 0);
+			opts->branch_exists =
+				validate_new_branchname(opts->new_branch, &buf, 0);
 		strbuf_release(&buf);
 	}
 
 	UNLEAK(opts);
-	if (opts.patch_mode || opts.pathspec.nr) {
-		int ret = checkout_paths(&opts, new_branch_info.name);
+	if (opts->patch_mode || opts->pathspec.nr) {
+		int ret = checkout_paths(opts, new_branch_info.name);
 		if (ret && dwim_remotes_matched > 1 &&
 		    advice_checkout_ambiguous_remote_branch_name)
 			advise(_("'%s' matched more than one remote tracking branch.\n"
@@ -1527,6 +1528,6 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 			       dwim_remotes_matched);
 		return ret;
 	} else {
-		return checkout_branch(&opts, &new_branch_info);
+		return checkout_branch(opts, &new_branch_info);
 	}
 }