Re: [GSOC PATCH] commit: avoid scanning trailing comments when 'core.commentChar' is "auto"
On Thu, Jun 26, 2025, at 15:22, Ayush Chandekar wrote:
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> When core.commentChar is set to "auto", Git selects a comment character
> by scanning the commit message contents and avoiding any character
> already present in the message.
>
> If the message still contains old conflict comments (starting with a
> comment character), Git assumes that character is in use and chooses a
> different one. As a result, those existing comment lines are no longer
> recognized as comments and end up being included in the final commit
> message.
>
> To avoid this, skip scanning the trailing comment block when selecting
> the comment character. This allows Git to safely reuse the original
> character when appropriate, keeping the commit message clean and free of
> leftover conflict information.
>
> Background:
>
> The "auto" value for core.commentchar was introduced in the commit
> `84c9dc2` (commit: allow core.commentChar=auto for character auto
> selection) but did not exhibt this issue at that time.
>
> The bug was introduced in commit `a6c2654` (rebase -m: fix --signoff
> with conflicts) where Git started writing conflict comments to the file
> at 'rebase_path_message()'.
>
> Mentored-by: Christian Couder <christian.couder@gmail.com>
> Mentored-by: Ghanshyam Thakkar <shyamthakkar001@gmail.com>
> Signed-off-by: Ayush Chandekar <ayu.chandekar@gmail.com>
> ---
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> diff --git a/t/t3418-rebase-continue.sh b/t/t3418-rebase-continue.sh
> index 127216f722..a8e89a250b 100755
> --- a/t/t3418-rebase-continue.sh
> +++ b/t/t3418-rebase-continue.sh
> @@ -328,6 +328,24 @@ test_expect_success 'there is no
> --no-reschedule-failed-exec in an ongoing rebas
> test_expect_code 129 git rebase --edit-todo
> --no-reschedule-failed-exec
> '
>
> +test_expect_success 'no change in comment character due to conflicts
> markers with core.commentChar=auto' '
> + test_commit base file &&
> + git checkout -b branch-a &&
> + test_commit A file &&
> + git checkout -b branch-b base &&
> + test_commit B file &&
> + test_must_fail git rebase branch-a &&
> + printf "B\nA\n" >file &&
> + git add file &&
> + write_script fake-editor <<-\EOF &&
> + exit 0
> + EOF
> + FAKE_EDITOR="$(pwd)/fake-editor" &&
> + GIT_EDITOR="\"\$FAKE_EDITOR\"" git -c core.commentChar=auto rebase --continue &&
How about
GIT_EDITOR="cat >actual"
Then you can `test_grep` on that. Like in
https://lore.kernel.org/git/5ed77fab-678d-4a06-bbd0-ea25462a7562@gmail.com/
> + # Check that "#" is still the comment character.
> + test_grep "# Changes to be committed:" .git/COMMIT_EDITMSG
Nit:
test_grep "^# Changes to be committed:$"
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> +'
> +
> test_orig_head_helper () {
> test_when_finished 'git rebase --abort &&
> git checkout topic &&
> --
> 2.49.0