bug#69188: bug#69233: 30.0.50; project-files + project-find-file is slow in large repositories

[Spencer Baugh <sbaugh@janestreet.com>]

Dmitry Gutov <dmitry@gutov.dev> writes:
> On 13/04/2024 05:34, Dmitry Gutov wrote:
>> Both options are relatively clunky, and the second one might also
>> fail to work when DIRS is non-nil (or would have to fall back to
>> absolute names anyway), so I'm leaning toward the first one. It
>> might also allow certain code to be written supporting both relative
>> and absolute names (e.g. a process call both binds default-directory
>> to root and keeps the file names as-is -- the relative ones would be
>> interpreted as such, the rest just as they are interpreted now).
>
> Here's how that change can look.
>
> The patch should demonstrate both the performance improvements for
> project-find-file and project-find-regexp, and some awkwardness in the
> implementation, chiefly due to backward compatibility.
>
> Guess more tests will be required, at the very least.

I see almost a 50% performance improvement with this patch in my large
private repository, once adding support for project-files-relative-names
in my internal project backend.  Seems great so far.

My benchmarking:

(let ((proj (project-current)))
  (list (benchmark-run 10 (let ((project-files-relative-names t)) (length (project-files proj))))
        (benchmark-run 10 (let ((project-files-relative-names nil)) (length (project-files proj))))))

((17.605295389 28 7.647366087000023)
 (29.918302167 57 19.246283027999993))