Hi Phillip,
On Tue, Jul 8, 2025 at 7:27 PM Phillip Wood <phillip.wood123@xxxxxxxxx> wrote:
>
> From: Phillip Wood <phillip.wood@xxxxxxxxxxxxx>
>
> When "core.commentString" is set to "auto" then "git commit"
> will automatically select the comment character ensuring that it
> does not the first character on any of the lines in the commit
> message. This was introduced by commit 84c9dc2c5a2 (commit: allow
> core.commentChar=auto for character auto selection, 2014-05-17) The
> motivation seems to be to avoid commenting out lines from the existing
> message when amending a commit that was created with a message from
> a file.
>
s/that it does not the first character/that it does not appear on the
first character?
> Unfortunately this feature does not work with:
>
> * commit message templates that contain comments.
>
> * prepare-commit-msg hooks that introduce comments.
>
> * "git commit --cleanup=strip --edit -F <file>" which means that it
> is incompatible with
>
> - the "fixup" and "squash" commands of "git rebase -i" as the
> comments added by those commands are then treated as part of the
> commit message.
>
> - the conflict comments added to the commit message by "git
> cherry-pick", "git rebase" etc. as these comments are then treated
> as part of the commit message.
>
> It is also ignored by "git notes" when amending a note.
>
> The issues with comments coming from a template, hook or file are a
> consequence of the design of this feature and are therefore hard to
> fix.
>
> As the costs of this feature outweigh the benefits deprecate it and
> remove it in Git 3.0. If someone comes up with some patches that fix all
> the issues in a maintainable way then I'd be happy to see this change
> reverted.
>
Nit: s/benefits deprecate/benefits, deprecate.
> The next commit will add some advice for users on how they can update
> their config settings.
>
> Signed-off-by: Phillip Wood <phillip.wood@xxxxxxxxxxxxx>
> ---
> Documentation/BreakingChanges.adoc | 4 ++++
> Documentation/config/core.adoc | 20 ++++++++++++++++++--
> builtin/commit.c | 4 ++++
> config.c | 4 ++++
> environment.c | 2 ++
> environment.h | 2 ++
> t/t3404-rebase-interactive.sh | 2 +-
> t/t7502-commit-porcelain.sh | 4 ++--
> 8 files changed, 37 insertions(+), 5 deletions(-)
>
> diff --git a/Documentation/BreakingChanges.adoc b/Documentation/BreakingChanges.adoc
> index 61bdd586b9e..f38ba1de6e4 100644
> --- a/Documentation/BreakingChanges.adoc
> +++ b/Documentation/BreakingChanges.adoc
> @@ -183,6 +183,10 @@ These features will be removed.
> timeframe, in preference to its synonym "--annotate-stdin". Git 3.0
> removes the support for "--stdin" altogether.
>
> +* Support for `core.commentString=auto` has been deprecated and will
> + be removed in Git 3.0.
> ++
> +cf. <xmqqa59i45wc.fsf@gitster.g>
>
> == Superseded features that will not be deprecated
>
> diff --git a/Documentation/config/core.adoc b/Documentation/config/core.adoc
> index 9fde1ab63a7..7133f00c38b 100644
> --- a/Documentation/config/core.adoc
> +++ b/Documentation/config/core.adoc
> @@ -531,9 +531,25 @@ core.commentString::
> commented, and removes them after the editor returns
> (default '#').
> +
> -If set to "auto", `git-commit` would select a character that is not
> +ifndef::with-breaking-changes[]
> +If set to "auto", `git-commit` will select a character that is not
> the beginning character of any line in existing commit messages.
> -+
> +Support for this value is deprecated and will be removed in Git 3.0
> +due to the following limitations:
> ++
> +--
> +* It is incompatible with adding comments in a commit message
> + template. This includes the conflicts comments added to
> + the commit message by `cherry-pick`, `merge`, `rebase` and
> + `revert`.
> +* It is incompatible with adding comments to the commit message
> + in the `prepare-commit-msg` hook.
> +* It is incompatible with the `fixup` and `squash` commands when
> + rebasing,
> +* It is not respected by `git notes`
> +--
> ++
> +endif::with-breaking-changes[]
> Note that these two variables are aliases of each other, and in modern
> versions of Git you are free to use a string (e.g., `//` or `⁑⁕⁑`) with
> `commentChar`. Versions of Git prior to v2.45.0 will ignore
> diff --git a/builtin/commit.c b/builtin/commit.c
> index fba0dded64a..8794b24572b 100644
> --- a/builtin/commit.c
> +++ b/builtin/commit.c
> @@ -683,6 +683,7 @@ static int author_date_is_interesting(void)
> return author_message || force_date;
> }
>
> +#ifndef WITH_BREAKING_CHANGES
> static void adjust_comment_line_char(const struct strbuf *sb)
> {
> char candidates[] = "#;@!$%^&|:";
> @@ -716,6 +717,7 @@ static void adjust_comment_line_char(const struct strbuf *sb)
> free(comment_line_str_to_free);
> comment_line_str = comment_line_str_to_free = xstrfmt("%c", *p);
> }
> +#endif /* WITH_BREAKING_CHANGES */
>
> static void prepare_amend_commit(struct commit *commit, struct strbuf *sb,
> struct pretty_print_context *ctx)
> @@ -912,8 +914,10 @@ static int prepare_to_commit(const char *index_file, const char *prefix,
> if (fwrite(sb.buf, 1, sb.len, s->fp) < sb.len)
> die_errno(_("could not write commit template"));
>
> +#ifndef WITH_BREAKING_CHANGES
> if (auto_comment_line_char)
> adjust_comment_line_char(&sb);
> +#endif /* WITH_BREAKING_CHANGES */
> strbuf_release(&sb);
>
> /* This checks if committer ident is explicitly given */
> diff --git a/config.c b/config.c
> index eb60c293ab3..f99496b16c0 100644
> --- a/config.c
> +++ b/config.c
> @@ -1537,14 +1537,18 @@ static int git_default_core_config(const char *var, const char *value,
> !strcmp(var, "core.commentstring")) {
> if (!value)
> return config_error_nonbool(var);
> +#ifndef WITH_BREAKING_CHANGES
> else if (!strcasecmp(value, "auto"))
> auto_comment_line_char = 1;
> +#endif /* WITH_BREAKING_CHANGES */
> else if (value[0]) {
> if (strchr(value, '\n'))
> return error(_("%s cannot contain newline"), var);
> comment_line_str = value;
> FREE_AND_NULL(comment_line_str_to_free);
> +#ifndef WITH_BREAKING_CHANGES
> auto_comment_line_char = 0;
> +#endif /* WITH_BREAKING_CHANGES */
> } else
> return error(_("%s must have at least one character"), var);
> return 0;
> diff --git a/environment.c b/environment.c
> index 7bf0390a335..6804380889f 100644
> --- a/environment.c
> +++ b/environment.c
> @@ -111,7 +111,9 @@ int protect_ntfs = PROTECT_NTFS_DEFAULT;
> */
> const char *comment_line_str = "#";
> char *comment_line_str_to_free;
> +#ifndef WITH_BREAKING_CHANGES
> int auto_comment_line_char;
> +#endif /* WITH_BREAKING_CHANGES */
>
> /* This is set by setup_git_directory_gently() and/or git_default_config() */
> char *git_work_tree_cfg;
> diff --git a/environment.h b/environment.h
> index 9a3d05d414a..871596afcef 100644
> --- a/environment.h
> +++ b/environment.h
> @@ -207,7 +207,9 @@ extern char *excludes_file;
> */
> extern const char *comment_line_str;
> extern char *comment_line_str_to_free;
> +#ifndef WITH_BREAKING_CHANGES
> extern int auto_comment_line_char;
> +#endif /* WITH_BREAKING_CHANGES */
>
> # endif /* USE_THE_REPOSITORY_VARIABLE */
> #endif /* ENVIRONMENT_H */
> diff --git a/t/t3404-rebase-interactive.sh b/t/t3404-rebase-interactive.sh
> index 6bac217ed35..ce0aebb9a7e 100755
> --- a/t/t3404-rebase-interactive.sh
> +++ b/t/t3404-rebase-interactive.sh
> @@ -1176,7 +1176,7 @@ test_expect_success 'rebase -i respects core.commentchar' '
> test B = $(git cat-file commit HEAD^ | sed -ne \$p)
> '
>
> -test_expect_success 'rebase -i respects core.commentchar=auto' '
> +test_expect_success !WITH_BREAKING_CHANGES 'rebase -i respects core.commentchar=auto' '
> test_config core.commentchar auto &&
> write_script copy-edit-script.sh <<-\EOF &&
> cp "$1" edit-script
> diff --git a/t/t7502-commit-porcelain.sh b/t/t7502-commit-porcelain.sh
> index b37e2018a74..65b4519a715 100755
> --- a/t/t7502-commit-porcelain.sh
> +++ b/t/t7502-commit-porcelain.sh
> @@ -956,13 +956,13 @@ test_expect_success 'commit --status with custom comment character' '
> test_grep "^; Changes to be committed:" .git/COMMIT_EDITMSG
> '
>
> -test_expect_success 'switch core.commentchar' '
> +test_expect_success !WITH_BREAKING_CHANGES 'switch core.commentchar' '
> test_commit "#foo" foo &&
> GIT_EDITOR=.git/FAKE_EDITOR git -c core.commentChar=auto commit --amend &&
> test_grep "^; Changes to be committed:" .git/COMMIT_EDITMSG
> '
>
> -test_expect_success 'switch core.commentchar but out of options' '
> +test_expect_success !WITH_BREAKING_CHANGES 'switch core.commentchar but out of options' '
> cat >text <<\EOF &&
> # 1
> ; 2
> --
> 2.49.0.897.gfad3eb7d210
>
Thanks for initiating this topic.
These changes look good to me.
Ayush
