Re: [PATCH v16 0/5] checkout: 'autostash' for branch switching

>   * Updated the git checkout and git switch docs to show the actual output
>     when using -m to carry local changes across a branch switch, and changed
>     "would carry" to "will carry".
>   * Rewrote the merge-conflict example in both docs to match the new, more
>     concise message printed on autostash conflicts.
>   * Replaced the show_unpack_errors flag and old_commit parameter in
>     merge_working_tree()/init_topts() with a plain quiet boolean, so the
>     caller decides directly whether to suppress unpack errors.
>   * Tightened the 'checkout -m with dirty tree' test by replacing a printf
>     with a heredoc.
>   * Made the 'checkout -m creates a recoverable stash on conflict' test also
>     assert the reflog subject of the new stash entry.
>   * Replaced two test_grep calls in the 'checkout -m which would overwrite
>     untracked file' test with a single test_cmp, which also catches a
>     regression where the "would be overwritten" message could end up printed
>     twice.

> Harald Nordgren (5):
>    stash: add --label-ours, --label-theirs, --label-base for apply
>    sequencer: allow create_autostash to run silently
>    sequencer: teach autostash apply to take optional conflict marker
>      labels
>    checkout: rollback lock on early returns in merge_working_tree
>    checkout -m: autostash when switching branches
> 
>   Documentation/git-checkout.adoc |  55 +++++------
>   Documentation/git-stash.adoc    |  11 ++-
>   Documentation/git-switch.adoc   |  36 ++++---
>   builtin/checkout.c              | 166 +++++++++++++++-----------------
>   builtin/commit.c                |   3 +-
>   builtin/merge.c                 |  15 ++-
>   builtin/stash.c                 |  28 ++++--
>   sequencer.c                     |  69 +++++++++----
>   sequencer.h                     |   7 +-
>   t/t3420-rebase-autostash.sh     |  16 +--
>   t/t3903-stash.sh                |  24 +++++
>   t/t7201-co.sh                   |  71 +++++++++++++-
>   t/t7600-merge.sh                |   3 +-
>   xdiff-interface.c               |  12 +++
>   xdiff-interface.h               |   1 +
>   xdiff/xmerge.c                  |   6 +-
>   16 files changed, 343 insertions(+), 180 deletions(-)
> 
> 
> base-commit: 94f057755b7941b321fd11fec1b2e3ca5313a4e0
> Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-2234%2FHaraldNordgren%2Fcheckout_autostash-v16
> Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-2234/HaraldNordgren/checkout_autostash-v16
> Pull-Request: https://github.com/git/git/pull/2234
> 
> Range-diff vs v15:
> 
>   1:  aba8e6a9dc = 1:  aba8e6a9dc stash: add --label-ours, --label-theirs, --label-base for apply
>   2:  89e0bfa803 = 2:  89e0bfa803 sequencer: allow create_autostash to run silently
>   3:  a428ce7328 = 3:  a428ce7328 sequencer: teach autostash apply to take optional conflict marker labels
>   4:  f358424085 = 4:  f358424085 checkout: rollback lock on early returns in merge_working_tree
>   5:  96b14db827 ! 5:  07d25fda91 checkout -m: autostash when switching branches
>       @@ Documentation/git-checkout.adoc: $ git checkout mytopic
>         
>        -You can give the `-m` flag to the command, which would try a
>        -three-way merge:
>       -+You can give the `-m` flag to the command, which would carry your local
>       ++You can give the `-m` flag to the command, which will carry your local
>        +changes to the new branch:
>         
>         ------------
>         $ git checkout -m mytopic
>        -Auto-merging frotz
>       ++Applied autostash.
>        +Switched to branch 'mytopic'
>       ++The following paths have local changes:
>       ++M	frotz
>         ------------
>         
>        -After this three-way merge, the local modifications are _not_
>       @@ Documentation/git-checkout.adoc: $ git checkout mytopic
>         
>        -When a merge conflict happens during switching branches with
>        -the `-m` option, you would see something like this:
>       -+When the `--merge` (`-m`) option is in effect and the locally
>       -+modified files overlap with files that need to be updated by the
>       -+branch switch, the changes are stashed and reapplied after the
>       -+switch.  If this process results in conflicts, a stash entry is saved
>       -+and made available in `git stash list`:
>       ++When the `--merge` (`-m`) option is given and the local changes
>       ++overlap with the changes in the branch we're switching to, the
>       ++changes are stashed and reapplied after the switch.  If this
>       ++process results in conflicts, the stash entry is saved and a
>       ++message is printed:
>         
>         ------------
>         $ git checkout -m mytopic
>       @@ Documentation/git-checkout.adoc: $ git checkout mytopic
>        -ERROR: Merge conflict in frotz
>        -fatal: merge program failed
>        -------------
>       -+Your local changes are stashed, however, applying it to carry
>       -+forward your local changes resulted in conflicts:
>       -
>       +-
>        -At this point, `git diff` shows the changes cleanly merged as in
>        -the previous example, as well as the changes in the conflicted
>        -files.  Edit and resolve the conflict and mark it resolved with
>        -`git add` as usual:
>       -+ - You can try resolving them now.  If you resolved them
>       -+   successfully, discard the stash entry with "git stash drop".
>       -
>       -+ - Alternatively you can "git reset --hard" if you do not want
>       -+   to deal with them right now, and later "git stash pop" to
>       -+   recover your local changes.
>       - ------------
>       +-
>       +-------------
>        -$ edit frotz
>        -$ git add frotz
>       --------------
>       -+
>       -+You can try resolving the conflicts now.  Edit the conflicting files
>       -+and mark them resolved with `git add` as usual, then run `git stash
>       -+drop` to discard the stash entry.  Alternatively, you can clear the
>       -+working tree with `git reset --hard` and recover your local changes
>       -+later with `git stash pop`.
>       ++Your local changes are stashed, however applying them
>       ++resulted in conflicts.  You can either resolve the conflicts
>       ++and then discard the stash with "git stash drop", or, if you
>       ++do not want to resolve them now, run "git reset --hard" and
>       ++apply the local changes later by running "git stash pop".
>       + ------------
>         
>         CONFIGURATION
>       - -------------
>        
>         ## Documentation/git-switch.adoc ##
>        @@ Documentation/git-switch.adoc: variable.
>       @@ Documentation/git-switch.adoc: $ git switch mytopic
>         
>        -You can give the `-m` flag to the command, which would try a three-way
>        -merge:
>       -+You can give the `-m` flag to the command, which would carry your local
>       ++You can give the `-m` flag to the command, which will carry your local
>        +changes to the new branch:
>         
>         ------------
>         $ git switch -m mytopic
>        -Auto-merging frotz
>       ++Applied autostash.
>        +Switched to branch 'mytopic'
>       ++The following paths have local changes:
>       ++M	frotz
>         ------------
>         
>        -After this three-way merge, the local modifications are _not_
>       @@ builtin/checkout.c: struct checkout_opts {
>         	char *name; /* The short name used */
>         	char *path; /* The full name of a real branch */
>        @@ builtin/checkout.c: static void setup_branch_path(struct branch_info *branch)
>       + 	branch->path = strbuf_detach(&buf, NULL);
>       + }
>         
>       - static void init_topts(struct unpack_trees_options *topts, int merge,
>       +-static void init_topts(struct unpack_trees_options *topts, int merge,
>       ++static void init_topts(struct unpack_trees_options *topts,
>         		       int show_progress, int overwrite_ignore,
>        -		       struct commit *old_commit)
>       -+		       struct commit *old_commit, bool show_unpack_errors)
>       ++		       bool quiet)
>         {
>         	memset(topts, 0, sizeof(*topts));
>         	topts->head_idx = -1;
>       @@ builtin/checkout.c: static void init_topts(struct unpack_trees_options *topts, i
>         	topts->update = 1;
>         	topts->merge = 1;
>        -	topts->quiet = merge && old_commit;
>       -+	topts->quiet = merge && old_commit && !show_unpack_errors;
>       ++	topts->quiet = quiet;
>         	topts->verbose_update = show_progress;
>         	topts->fn = twoway_merge;
>         	topts->preserve_ignored = !overwrite_ignore;
>       @@ builtin/checkout.c: static void init_topts(struct unpack_trees_options *topts, i
>         static int merge_working_tree(const struct checkout_opts *opts,
>         			      struct branch_info *old_branch_info,
>         			      struct branch_info *new_branch_info,
>       --			      int *writeout_error)
>       -+			      int *writeout_error,
>       -+			      bool show_unpack_errors)
>       ++			      bool quiet,
>       + 			      int *writeout_error)
>         {
>         	int ret;
>       - 	struct lock_file lock_file = LOCK_INIT;
>        @@ builtin/checkout.c: static int merge_working_tree(const struct checkout_opts *opts,
>       + 		}
>         
>         		/* 2-way merge to the new branch */
>       - 		init_topts(&topts, opts->merge, opts->show_progress,
>       +-		init_topts(&topts, opts->merge, opts->show_progress,
>        -			   opts->overwrite_ignore, old_branch_info->commit);
>       -+			   opts->overwrite_ignore, old_branch_info->commit,
>       -+			   show_unpack_errors);
>       ++		init_topts(&topts, opts->show_progress,
>       ++			   opts->overwrite_ignore, quiet);
>         		init_checkout_metadata(&topts.meta, new_branch_info->refname,
>         				       new_branch_info->commit ?
>         				       &new_branch_info->commit->object.oid :
>       @@ builtin/checkout.c: static int switch_branches(const struct checkout_opts *opts,
>         	if (do_merge) {
>        -		ret = merge_working_tree(opts, &old_branch_info, new_branch_info, &writeout_error);
>        +		ret = merge_working_tree(opts, &old_branch_info, new_branch_info,
>       -+					 &writeout_error, false);
>       ++					 opts->merge, &writeout_error);
>        +		if (ret == MERGE_WORKING_TREE_UNPACK_FAILED && opts->merge) {
>        +			strbuf_addf(&autostash_msg,
>        +				    "autostash while switching to '%s'",
>       @@ builtin/checkout.c: static int switch_branches(const struct checkout_opts *opts,
>        +					     autostash_msg.buf, true);
>        +			created_autostash = 1;
>        +			ret = merge_working_tree(opts, &old_branch_info, new_branch_info,
>       -+						 &writeout_error, true);
>       ++						 false, &writeout_error);
>        +		}
>        +		if (created_autostash) {
>        +			if (opts->conflict_style >= 0) {
>       @@ t/t7201-co.sh: test_expect_success 'checkout -m with dirty tree' '
>         	test "$(git symbolic-ref HEAD)" = "refs/heads/side" &&
>         
>        -	printf "M\t%s\n" one >expect.messages &&
>       -+	printf "The following paths have local changes:\nM\t%s\n" one >expect.messages &&
>       ++	cat >expect.messages <<-\EOF &&
>       ++	The following paths have local changes:
>       ++	M	one
>       ++	EOF
>         	test_cmp expect.messages messages &&
>         
>         	fill "M	one" "A	three" "D	two" >expect.main &&
>       @@ t/t7201-co.sh: test_expect_success 'checkout --merge --conflict=diff3 <branch>'
>        +	test_grep "git stash drop" actual &&
>        +	test_grep "git stash pop" actual &&
>        +	test_grep "The following paths have local changes" actual &&
>       -+	git show --format=%B --diff-merges=1 refs/stash >actual &&
>       ++	git log -p -1 --format="%gs%n%B" -g --diff-merges=1 refs/stash >actual &&
>        +	sed /^index/d actual >actual.trimmed &&
>        +	cat >expect <<-EOF &&
>       ++	autostash while switching to ${SQ}side${SQ}
>        +	On main: autostash while switching to ${SQ}side${SQ}
>        +
>        +	diff --git a/one b/one
>       @@ t/t7201-co.sh: test_expect_success 'checkout --merge --conflict=diff3 <branch>'
>        +	>another-file.t &&
>        +	fill 1 2 3 4 5 >one &&
>        +	test_must_fail git checkout -m @{-1} 2>err &&
>       -+	test_grep "would be overwritten by checkout" err &&
>       -+	test_grep "another-file.t" err
>       ++	q_to_tab >expect <<-\EOF &&
>       ++	error: The following untracked working tree files would be overwritten by checkout:
>       ++	Qanother-file.t
>       ++	Please move or remove them before you switch branches.
>       ++	Aborting
>       ++	Applied autostash.
>       ++	EOF
>       ++	test_cmp expect err
>        +'
>        +
>         test_expect_success 'switch to another branch while carrying a deletion' '
>