Subject: Re: [PATCH 0/2] breaking-changes: deprecate support for core.commentChar=auto

From: Phillip Wood <[email-masked]>
Date: Wed, 9 Jul 2025 10:38:19 +0100

On 08/07/2025 19:51, Junio C Hamano wrote:
> Phillip Wood <[email-masked]> writes:
> 
>> From: Phillip Wood <[email-masked]>
>>
>> This series implements the plan to deprecate and remove support for
>> core.commentChar=auto outlined in [1]. This feature has been the
>> source of a couple of bug reports recently [2,3] and as explained in
>> the first patch the design is tricky to fix. When git sees the
>> deprecated config setting it will print advice like the example below
>> to help the user either remove the setting or set a custom comment
>> string.

With hindsight I should have been clearer here that the advice given is 
based on the user's config settings. In this case the files look like

~/.gitconfig:
     [core]
         commentChar = auto

~/$XDG_COMFIG/HOME/git/config
     [core]
         commentString = %
         commentString = !
         commentChar = auto

>> hint: Support for 'core.commentChar=auto' is deprecated and will be removed in git 3.0
>> hint:
>> hint: To use the default comment string (#) please run
>> hint:
>> hint:     git config unset --file ~/.config/git/config --all core.commentString
>> hint:     git config unset --file ~/.config/git/config core.commentChar
>> hint:     git config unset --global core.commentChar
> 
> We'd need to clear both variants from all scopes, wouldn't we?
> 
> 	for scope in "" --local --global --worktree
> 	do
> 		for variant in commentString commentChar
> 		do
> 			git config unset $scope --all core.$variant
> 		done
> 	done

The advice includes commands to clear all the scopes that are set. It 
correctly handles include files and correctly handles cases where both 
.gitconfig and $XDG_CONFIG_HOME/git/config exist (where "git config 
unset --global <key>" will only unset <key> in ~/.gitconfig)

>> hint:
>> hint: To set a custom comment string please run
>> hint:
>> hint:     git config set --global core.commentChar <comment string>
>> hint:
>> hint: where '<comment string>' is the string you wish to use.
> 
> I do not particulary find it sensible to nudge users to use the same
> commentChar across all projects with possibly different project
> conventions by suggesting use of the --global option here.

The advice will recommend a command that updates commentChar in the 
scope where it is currently set so if it is set globally it will not 
prompt you to set it locally in each repository and if it is set locally 
it will prompt you to update it there.
> It would be necessary to special case "auto" after 3.0 boundary
> anyway, whether we (1) die when we notice the value is set to
> "auto", and refuse to work until the user chooses a comment char, or
> (2) use "#" or something hardcoded.  Either would be better than
> using literal string "auto" as comment char.

We can do that if you've changed your view from 
<[email-masked]>

> So, a simpler approach might be to treat literal string "auto" as if
> "#" was specified under WITH_BREAKING_CHANGES so that the end-user
> does not have to do anything when they want to "revert" to the
> default comment string.  Then we do not have to give any large text
> like the above.  We can instead say something like
> 
> 	The 'auto' setting of core.commentChar (or core.commentString)
> 	will change its meaning in Git 3.0 and later and will always
> 	use the default '#'.

That's certainly simpler for us but it does not help the user to update 
their config. Presumably they're using the auto commentchar because '#' 
does not work for them.

Thanks

Phillip
> Hmm?
> 
>> [1] https://lore.kernel.org/git/[email-masked]
>> [2] https://lore.kernel.org/git/[email-masked]
>> [3] https://lore.kernel.org/git/[email-masked]
>>
>> Base-Commit: f0135a9047ca37d4d117dcf21f7e3e89fad85d00
>> Published-As: https://github.com/phillipwood/git/releases/tag/pw%2Fremove-auto-comment-char%2Fv1
>> View-Changes-At: https://github.com/phillipwood/git/compare/f0135a904...83d0d3ece
>> Fetch-It-Via: git fetch https://github.com/phillipwood/git pw/remove-auto-comment-char/v1
>>
>>
>> Phillip Wood (2):
>>    breaking-changes: deprecate support for core.commentString=auto
>>    commit: print advice when core.commentString=auto
>>
>>   Documentation/BreakingChanges.adoc |   4 +
>>   Documentation/config/core.adoc     |  20 ++-
>>   builtin/commit.c                   | 192 +++++++++++++++++++++++++++++
>>   config.c                           |   4 +
>>   environment.c                      |   2 +
>>   environment.h                      |   2 +
>>   t/t3404-rebase-interactive.sh      |   2 +-
>>   t/t7502-commit-porcelain.sh        |  32 ++++-
>>   8 files changed, 252 insertions(+), 6 deletions(-)