Re: Adding git-commit highlight mode?

[Stefan Kangas <stefankangas@gmail.com>]

Konstantin Kharlamov <Hi-Angel@yandex.ru> writes:

> On Thu, 2025-01-02 at 21:01 +0200, Eli Zaretskii wrote:
>> > From: Konstantin Kharlamov <Hi-Angel@yandex.ru>
>> > Date: Thu, 02 Jan 2025 21:30:53 +0300
>> >
>> > Hi, just wanted to ask this before potentially taking on the
>> > initiative
>> > to only find the code will get rejected.
>> >
>> > I think a ballpark estimate of 90% of Git usage among CVSes in the
>> > modern world is fair to assume.
>> >
>> > But Emacs seems to be the only widely popular editor that still
>> > doesn't
>> > provide OOTB at least syntax highlight for git-commit format. So,
>> > does
>> > anyone have opposition to adding a major mode that would be bound
>> > to
>> > filenames like `COMMIT_EDITMSG` and others, and would provide the
>> > aforementioned highlight?

It would be great to have something like that in Emacs by default,
indeed.  Even a simple mode with syntax highlighting would go a long
way.

Note that there is some prior work here, see `git-commit-mode' in
`magit`.  However, AFAIU, we recommend not looking at the implementation
if you want to implement something like it, for reasons of copyright.
The reason is that once you look at its implementation it's hard to
write something original enough to be able to copyright assign the
result to the Free Software Foundation, and even if it is original it
can still (under some circumstances) be considered a derivative work of
the code you have looked at.

You can look at its docstrings though.  Let me know if this is
interesting, and I'll happily share it with you off-list.

I'm copying in Jonas Bernoulli, in case he has any comments.

>> Do you plan to make this mode be descendant of change-log-mode?
>> something else?
>
> I thought of deriving from text-mode. I don't know much of change-log-
> mode besides what it says in the mode title and now that I'm looking at
> mode description it also sounds pretty vague. So… I could derive it
> from change-log-mode if you think it's useful, but I'd rely on your
> judgment here 😊

`change-log-mode` implements the anachronistic ChangeLog format favored
by GNU.  If the idea is to be useful to the 90% of the world that uses
Git, I'd recommend against inheriting from `change-log-mode`, because
99.99% or so of Git users do not use that format.

Granted, that figure might be something more like 99.9% when it comes to
GNU Emacs users specifically.