bug#64735: 29.0.92; find invocations are ~15x slower because of ignores

[Eli Zaretskii]

> Cc: Ihor Radchenko <yantar92@posteo.net>, 64735@debbugs.gnu.org
> Date: Sun, 23 Jul 2023 00:01:28 +0300
> From: Dmitry Gutov <dmitry@gutov.dev>
> 
> On 22/07/2023 09:39, Po Lu wrote:
> > 
> > Programs that use find should fall back to directory-file-recursively
> > when any of the situations above are detected.
> 
> Perhaps if someone implements support for IGNORE entries (wildcards) in 
> that function, it would be easy enough to do that fallback.

Shouldn't be hard, since it already filters some of them:

    (dolist (file (sort (file-name-all-completions "" dir)
                        'string<))
      (unless (member file '("./" "../"))  <<<<<<<<<<<<<<<<<<<

Even better: compute completion-regexp-list so that IGNOREs are
filtered by file-name-all-completions in the first place.

Patches welcome.