bug#68864: 30.0.50; project-find-regexp fails on Alpine

[Dmitry Gutov <dmitry@gutov.dev>]

On 01/02/2024 05:38, john muhl via Bug reports for GNU Emacs, the Swiss 
army knife of text editors wrote:
> The grep on Alpine does not support the --null option.
> 
>    $ grep --null test *
>    grep: unrecognized option: null
>    BusyBox v1.36.1 (2024-01-16 17:10:30 UTC) multi-call binary.
> 
> To reproduce:
> 
>    emacs -Q
>    M-: (project-find-regexp "test")
> 
> Debugger entered--Lisp error: (user-error "Search failed with status 123: grep: unrecognized option: null")
>    signal(user-error ("Search failed with status 123: grep: unrecognized option: null"))

Hi!

That's a problem: apparently it does indeed not support --null or -Z: 
https://boxmatrix.info/wiki/Property:grep

There is another flag we could use, which seems to have a similar enough 
effect: -z. But from what I can tell, it would make OpenBSD unsupported: 
https://man.openbsd.org/grep

Perhaps it would be best to just file a feature request for busybox's 
support for --null/-Z. Better ideas welcome.

In the meantime, you can customize the entry for 'grep' in 
xref-search-program-alist to use -z.