bug#30559: 26.0.91; grep-use-null-filename-separator customization

[Eli Zaretskii <eliz@gnu.org>]

> From: Juri Linkov <juri@linkov.net>
> Cc: 30559@debbugs.gnu.org
> Date: Fri, 02 Mar 2018 00:45:27 +0200
> 
> Sorry, I forgot to do the same for zrgrep.  I already noticed earlier
> that grep-use-null-filename-separator let-binding is missing here,
> but forgot to test this to affirm the necessity to fix zrgrep too.
> So this fix is needed for the release branch.
> 
> Eli, is it OK to push this patch to emacs-26 as well?
> 
> diff --git a/lisp/progmodes/grep.el b/lisp/progmodes/grep.el
> index 755c9c7..9b6ebee 100644
> --- a/lisp/progmodes/grep.el
> +++ b/lisp/progmodes/grep.el
> @@ -1184,6 +1184,7 @@ zrgrep
>  	   ;; by `grep-compute-defaults'.
>  	   (grep-find-template nil)
>  	   (grep-find-command nil)
> +	   (grep-use-null-filename-separator nil)
>  	   (grep-host-defaults-alist nil)
>  	   ;; Use for `grep-read-files'
>  	   (grep-files-aliases '(("all" . "* .*")

Yes, but please add a comment there explaining why this is done.  (And
AFAIU, our auto-detect stuff needs fixing, if it must be overridden
like that.)

Thanks.