Re: emacs-30 f0daa2f2153: Conservative heuristic for tree-sitter parser ranges (bug#73324)

[Kévin Le Gouguec]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Kévin Le Gouguec <kevin.legouguec@gmail.com>
>> Cc: casouri@gmail.com,  luangruo@yahoo.com,  stefankangas@gmail.com,
>>   emacs-devel@gnu.org
>> Date: Mon, 23 Sep 2024 19:24:45 +0200
>> 
>> > Isn't it a bug in magit that it doesn't do something like that
>> > already?  Fill column is just the tip of an iceberg, because a log
>> > message is generally human-readable text, and so should benefit from
>> > other features of Text mode and its descendants, like spell-checking
>> > etc.
>> 
>> It does try to do "something like that"; AFAIU the two main knobs are:
>> 
>> * git-commit-major-mode lets users pick their preferred text-adjacent
>> major mode (or it lets maintainers choose it, e.g. setting that variable
>> in a checked-in .dir-locals.el; the default is text-mode),
>> 
>> * git-commit-setup-hook lets users turn on useful log-editing features;
>> the defcustom includes various opt-in functions.  Robert mentioned
>> magit-generate-changelog; there's also git-commit-turn-on-flyspell and
>> bug-reference-mode.
>> 
>> (There's also a mysterious git-commit-setup-changelog-support that
>> checks for
>> 
>>   (fboundp 'log-indent-fill-entry) ; New in Emacs 27
>> 
>> but I can't find any trace of log-indent-fill-entry in the tree so not
>> sure what that's about)
>
> That sounds to me like a heap of patches when just having a full-blown
> mode like VC does would have done the job cleanly and seamlessly.

That's how it was 10 years ago: there was a single major mode,
git-commit-mode, which "did it all" (setup emacsclient as git's EDITOR,
setup font-lock, provide key bindings, etc).  Then the decision was
taken to move to configurable-major-mode-plus-hook.

The commit log for that change¹ focuses on the technical details over
the motivation, but looking at the current defcustom's selection of
major modes, I guess the use-case is obvious - let people pick their
preferred markup for authoring messages, and tuck all the "VC-specific
extra features" under a dedicated minor mode & hook.

>> So what's "missing" from Magit's git-commit.el is a knob dedicated to
>> the fill-column for commit messages.
>
> I'm quite sure that soon enough someone will come with more "missing"
> stuff.  I still think they should use something very similar to
> log-edit-mode there.  It doesn't make much sense not to.  E.g., the
> .dir-locals settings would have been in effect for magit users as
> well.

Right.  And in principle users should be able to opt-in to log-edit-mode
(or vc-git-log-edit-mode?) by configuring git-commit-major-mode.

I just don't expect that to be seamless - because (AFAIR; apologies for
inaccuracies) log-edit-mode depends on callbacks set by vc-$BACKEND.el,
which in turn depend on bookkeeping usually managed by vc.el commands;
Magit steers mostly clear of that bookkeeping.

tl;dr I don't disagree but I don't see log-edit-mode integration into
Magit to be the path of least resistance.

(That shouldn't stop anyone from trying though, or submit a feature
request; this is all just my 2¢ as a {heavy Magit,occasional VC} user)


¹ 2014-03-18 "git-commit: allow use of arbitrary major mode" (feb58998)
  
https://github.com/magit/magit/commit/feb58998fc128824728959695a9448e7752c2ca3.patch