From: Erick Mattos <erick.mattos@gmail.com>
Date: Tue, 16 Mar 2010 18:19:44 GMT
Subject: [PATCH v3] git checkout -b: unparent the new branch with -o
Message-ID: <1268763584-14164-1-git-send-email-erick.mattos@gmail.com>

Sometimes it is interesting to start a new unparented branch in an
existing repository.

The new -o/--orphan is intended to solve this situation allowing the
creation of a new branch unparented to any other.

After the 'checkout -o -b' the new branch is not saved until committed.
Before committing you should 'git rm -rf' anything which is not going to
take part in the new branch and change the work tree and index the way
you want it to be since they remain untouched as before checkout
command.

There are two potential work flows where this feature is most useful:

(1) "mostly common paths" work flow;
(2) "no common paths" work flow;

Signed-off-by: Erick Mattos <erick.mattos@gmail.com>
---

Major rewrite to conform to Junio's demands.

Now after checkout to the new unparented branch, the index and the work tree
remain unchanged.

 Documentation/git-checkout.txt |   13 ++++++++++
 builtin/checkout.c             |   10 ++++++-
 t/t2017-checkout-orphan.sh     |   49 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 70 insertions(+), 2 deletions(-)
 create mode 100755 t/t2017-checkout-orphan.sh

diff --git a/Documentation/git-checkout.txt b/Documentation/git-checkout.txt
index 37c1810..92562ce 100644
--- a/Documentation/git-checkout.txt
+++ b/Documentation/git-checkout.txt
@@ -9,6 +9,7 @@ SYNOPSIS
 --------
 [verse]
 'git checkout' [-q] [-f] [-m] [<branch>]
+'git checkout' [-q] [-f] [-m] [-b <new_branch> [-o]]
 'git checkout' [-q] [-f] [-m] [-b <new_branch>] [<start_point>]
 'git checkout' [-f|--ours|--theirs|-m|--conflict=<style>] [<tree-ish>] [--] <paths>...
 'git checkout' --patch [<tree-ish>] [--] [<paths>...]
@@ -26,6 +27,13 @@ use the --track or --no-track options, which will be passed to `git
 branch`.  As a convenience, --track without `-b` implies branch
 creation; see the description of --track below.
 
+When using -b, it is possible to use the option -o to set the new branch
+as unparented thus unrelated to the previous branch.  The new branch is
+not saved until committed.  But before committing you should first do
+'git rm -rf' anything which is not going to take part in the new branch
+and change the work tree and index the way you want it to be since they
+remain untouched as before checkout command.
+
 When <paths> or --patch are given, this command does *not* switch
 branches.  It updates the named paths in the working tree from
 the index file, or from a named <tree-ish> (most often a commit).  In
@@ -86,6 +94,11 @@ 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.
 
+-o::
+--orphan::
+	When creating a new branch, set it up as unparented thus
+	unrelated to the previous branch.
+
 -l::
 	Create the new branch's reflog; see linkgit:git-branch[1] for
 	details.
diff --git a/builtin/checkout.c b/builtin/checkout.c
index acefaaf..405de7e 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -34,6 +34,7 @@ struct checkout_opts {
 
 	const char *new_branch;
 	int new_branch_log;
+	int new_branch_orphan;
 	enum branch_track track;
 };
 
@@ -491,8 +492,9 @@ static void update_refs_for_switch(struct checkout_opts *opts,
 	struct strbuf msg = STRBUF_INIT;
 	const char *old_desc;
 	if (opts->new_branch) {
-		create_branch(old->name, opts->new_branch, new->name, 0,
-			      opts->new_branch_log, opts->track);
+		if (!opts->new_branch_orphan)
+			create_branch(old->name, opts->new_branch, new->name, 0,
+				      opts->new_branch_log, opts->track);
 		new->name = opts->new_branch;
 		setup_branch_path(new);
 	}
@@ -629,6 +631,7 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 	struct option options[] = {
 		OPT__QUIET(&opts.quiet),
 		OPT_STRING('b', NULL, &opts.new_branch, "new branch", "branch"),
+		OPT_BOOLEAN('o', "orphan", &opts.new_branch_orphan, "make the new branch unparented"),
 		OPT_BOOLEAN('l', NULL, &opts.new_branch_log, "log for new branch"),
 		OPT_SET_INT('t', "track",  &opts.track, "track",
 			BRANCH_TRACK_EXPLICIT),
@@ -677,6 +680,9 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 		opts.new_branch = argv0 + 1;
 	}
 
+	if (opts.new_branch_orphan && !opts.new_branch)
+		die("-o is used only with -b");
+
 	if (conflict_style) {
 		opts.merge = 1; /* implied */
 		git_xmerge_config("merge.conflictstyle", conflict_style, NULL);
diff --git a/t/t2017-checkout-orphan.sh b/t/t2017-checkout-orphan.sh
new file mode 100755
index 0000000..c1b77ac
--- /dev/null
+++ b/t/t2017-checkout-orphan.sh
@@ -0,0 +1,49 @@
+#!/bin/sh
+#
+# Copyright (c) 2010 Erick Mattos
+#
+
+test_description='git checkout -b
+
+Tests for -o functionality.'
+
+. ./test-lib.sh
+
+TEST_FILE=foo
+
+test_expect_success 'Setup' '
+	echo "initial" >"$TEST_FILE" &&
+	git add "$TEST_FILE" &&
+	git commit -m "First Commit"
+'
+
+test_expect_success '-b without -o checkout into a new clone branch' '
+	test_tick &&
+	echo "Test 1" >>"$TEST_FILE" &&
+	git add "$TEST_FILE" &&
+	git commit -m "Second Commit" &&
+	git log --pretty=oneline >base &&
+	git checkout -b alpha &&
+	test "alpha" = "$(git symbolic-ref HEAD | sed "s,.*/,,")" &&
+	git log --pretty=oneline >actual &&
+	test_cmp base actual
+'
+
+test_expect_success '-b with -o checkout into an orphan branch' '
+	git checkout -ob beta &&
+	test_must_fail PAGER= git log >/dev/null 2>/dev/null &&
+	test "beta" = "$(git symbolic-ref HEAD | sed "s,.*/,,")" &&
+	test_tick &&
+	echo "Test 2" >>"$TEST_FILE" &&
+	git add "$TEST_FILE" &&
+	git commit -m "Third Commit" &&
+	git log --pretty=oneline >actual &&
+	test 1 -eq $(wc -l actual | sed "s/ .*//") &&
+	! test_cmp base actual
+'
+
+test_expect_success '-o must be rejected without -b' '
+	test_must_fail git checkout -o alpha
+'
+
+test_done
-- 
1.7.0.2.274.gc8f05