Eli Zaretskii <eliz@gnu.org> writes:

>> From: Kévin Le Gouguec <kevin.legouguec@gmail.com>
>> Cc: 76187@debbugs.gnu.org,  eggert@cs.ucla.edu
>> Date: Thu, 13 Feb 2025 23:58:21 +0100
>> 
>> Kévin Le Gouguec <kevin.legouguec@gmail.com> writes:
>> 
>> > FWIW, with that last patch I posted, the test has been passing on repeat
>> > for 3h (47k iterations) and counting.  Maybe we have a winner?
>> 
>> 4h10min, 66k iterations, no failures.  Stopping the count because this
>> brain needs zzz's.
>> 
>> > Let me know if it looks acceptable, I'll add commentary & a changelog
>> > entry.
>> 
>> Done; attached for your consideration.
>
> I'm okay with this if Dmitry agrees.

For the sake of intellectual honesty (and to prove, if need be, that I
am a clown), while I do still prefer getting vc-dir out of the equation
for the purpose of testing vc-git-dir-extra-headers (and so, applying
the patch to which you reply),

I should note that with the alternative attached patch, the test has
been passing 7k times for 1h, with reassuring traces such as:

    Running in foreground: git --no-pager clone /tmp/emacs-test-Aoc9gk-vc-git/ /tmp/emacs-test-qRZ6nt-vc-git/ .
    Done (status=0): git --no-pager clone /tmp/emacs-test-Aoc9gk-vc-git/ /tmp/emacs-test-qRZ6nt-vc-git/ .
    Running in foreground: git --no-pager config --get remote.origin.url
    Done (status=0): git --no-pager config --get remote.origin.url
    Running in background: git --no-pager update-index --refresh .
    Done in background: git --no-pager update-index --refresh .
    Running in background: git --no-pager diff-index --relative -z -M HEAD -- .
    Done in background: git --no-pager diff-index --relative -z -M HEAD -- .
    Running in background: git --no-pager ls-files -z -u -- .
    Done in background: git --no-pager ls-files -z -u -- .
    Running in background: git --no-pager ls-files -z -o --exclude-standard -- .
    Done in background: git --no-pager ls-files -z -o --exclude-standard -- .
    Paused 50 ms waiting for vc-dir-busy
    Running in foreground: git --no-pager checkout -b feature/foo master .

IOW waiting for vc-dir-busy *after* invoking vc-dir seems to work fine,
which makes complete sense, and I am not sure why I never thought about
this in the first place?

Let me know if we favor this approach, in which case I'll add the
finishing touches on that patch (docstring, changelog).