bug#46859: 28.0.50; [PATCH]: Add option to truncate long lines in xref.el

[Gregory Heytings]

> 'find' is rarely the fastest way to list all the files in the project. 
> Have you timed it alone?
>
> 'git ls-files' is usually much faster, and that's what 'project-files' 
> uses under the covers.

I don't see a big difference: find takes 0.006 s, git ls-files 0.002 s. 
Okay, that's three times slower, but those four milliseconds are not the 
bottleneck here.  I just ran some of the timing tests again, and they are 
about ten milliseconds faster with git ls-files, which is not a huge 
difference.  (Of course I do not object to the use of git ls-files.)

> So if you redo your test with 'project-find-regexp' as I suggested, you 
> might discover a different slowdown multiplier.

I wanted to first time these things outside of Emacs, it seems to me that 
it's a more objective comparison.