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

[Eli Zaretskii]

> From: Ihor Radchenko <yantar92@posteo.net>
> Cc: sbaugh@catern.com, sbaugh@janestreet.com, dmitry@gutov.dev,
>  michael.albinus@gmx.de, rms@gnu.org, 64735@debbugs.gnu.org
> Date: Sun, 23 Jul 2023 09:34:20 +0000
> 
> The only callback paradigm I know of in Emacs is something like process
> sentinels. Do you have something else in mind?

Think about an API that is passed a function, and calls that function
when appropriate, to perform caller-defined processing of the stuff
generated by the API's implementation.  That function is what I
referred to as "callback".