bug#54608: 29.0.50; xref-search-program-alist: support ugrep

[Dmitry Gutov]

On 28.03.2022 18:43, Manuel Uberti via Bug reports for GNU Emacs, the 
Swiss army knife of text editors wrote:
> I tried `(benchmark-run (project-find-regexp "torvalds"))` in the Linux 
> kernel code.
>
> With grep: (3.628388951 6 0.3137041489999959)
> With ugrep: (2.664314312 6 0.31696058299999663)

This is pretty good.

Did you run them a bunch of times? All subsequent searches after the 
first one are usually faster because of "warm" filesystem cache.