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

["Kévin Le Gouguec" <kevin.legouguec@gmail.com>]

Yuan Fu <casouri@gmail.com> writes:

>> On Sep 21, 2024, at 10:43 PM, Po Lu <luangruo@yahoo.com> wrote:
>> 
>> Stefan Kangas <stefankangas@gmail.com> writes:
>> 
>>>> Please fill ChangeLog entries in commit messages to a width of 64
>>>> columns, not 71 or 72, as here.
>>> 
>>> I don't want to get into another argument about this, but I don't see
>>> any problem with the above formatting, FWIW.
>>> 
>>> In any case, I really don't think it is a good use of our time to police
>> 
>> It is a good (and a exceedingly slight) use of my time.
>> 
>>> the recently introduced default of 64 columns here.  We never did that
>>> before, when the default in `vc-git-log-edit-mode' was 70 characters,
>>> and there is no reason to start doing it now.
>> 
>> That point is moot when most of us were self-consciously observing this
>> standard before it was formalized in .dir-locals.el.
>
> I took a look and it’s set for log-edit-mode only. It would be nice if magit can pick it up. I’m sure a lot of people (me included) use magit for developing Emacs. The only problem is magit’s commit message editing buffer doesn’t have a special major mode. It does git-commit-mode which is a minor mode, and runs git-commit-setup-hook. But I’m not sure how to edit dir-locals to set fill-column using a hook or minor mode.

Kludge from my personal config reproduced below¹, if it can help.  It
adds a function to git-commit-setup-hook that sets fill-column when it
detects that one of the remotes is Emacs's Savannah repo.

Thinking more about it, and considering the existence of the
git-commit-major-mode variable, I guess one could also

1) define a major mode derived from text-mode in their personal config;
2) add a .dir-locals-2.el file to their Emacs checkout that sets
git-commit-major-mode to that-new-mode, and fill-column to
  *checks config*
63
  *checks discussion*
^W64
  *ponders git-blaming to see what Past Self has to say for himself*
  *looks at the time*
  *you're off the hook, Past Self*
for that-new-mode.

Thinking *more* about it, setting git-commit-major-mode to log-edit-mode
in .dir-locals-2.el sounds like TRT in theory; in practice though I bet
it would lead to "interesting" fireworks².


¹

```
(defun my/git-upstreams ()
  ;; TODO: memoize, perhaps?
  (seq-uniq
   (seq-keep
    (lambda (remote-desc)
      (and (string-match "\\`.*\t\\(.*\\) (fetch)\\'" remote-desc)
           (match-string 1 remote-desc)))
    (process-lines "git" "remote" "-v"))))

(defun my/emacs-repo-p (upstreams)
  "Guess whether we are working in the Emacs repository.
UPSTREAMS is a list of fetch URLs."
  (member "https://git.savannah.gnu.org/git/emacs.git" upstreams))

(defvar my/git-commit-fill-columns
  '((my/emacs-repo-p . 63)))

(cl-defun my/git-commit-maybe-set-fill-column ()
  (let ((remotes (my/git-upstreams)))
    (pcase-dolist (`(,pred . ,column) my/git-commit-fill-columns)
      (when (funcall pred remotes)
        (cl-return-from my/git-commit-maybe-set-fill-column
          (setq fill-column column))))))

(add-hook
 'git-commit-setup-hook
 'my/git-commit-maybe-set-fill-column)
```

² Off the top of my head:

* bindings conflicting, e.g. log-edit-done vs with-editor-finish:
guessing the minor mode wins in that case… 🫣

* log-edit-generate-changelog-from-diff being ineffectual because
log-edit-diff-function is not set up: something to kludge around, though
Magit does also provide magit-commit-add-log from the diff buffer 🤷