bug#59888: [PATCH] Add 'grep-use-headings'

[Juri Linkov]

> +(defvar grep-heading-regexp
> +  (rx bol
> +      (or
> +       (group-n 2
> +         (group-n 1 (+ (not (any 0 ?\n))))
> +         0)
> +       (group-n 2
> +        (group-n 1 (+? nonl))
> +        (any ?: ?- ?=)))
> +      (+ digit)
> +      (any ?: ?- ?=))

I wonder what is the reason for this regexp to be different
from grep-regexp-alist?  Especially with such additional characters
as ?- and ?=.  This mismatch causes wrong handling of files when
file names contain these characters.