Re: [Emacs-diffs] master 644cdd1: Use grep's --null option (Bug#6843)

[Dmitry Gutov <dgutov@yandex.ru>]

Hey Noam,
Sorry I'm late to the party. Some questions below. Thanks.

On 7/20/17 3:02 AM, Noam Postavsky wrote:
> branch: master
> commit 644cdd1aa0a10dbfffa3b9b4c7a97f8cddded0b8
> Author: Noam Postavsky <npostavs@gmail.com>
> Commit: Noam Postavsky <npostavs@gmail.com>
...
> +*** Grep commands will now use GNU grep's '--null' option if
> +available, which allows distinguishing the filename from contents if
> +they contain colons.  This can be controlled by the new custom option
> +'grep-use-null-filename-separator'.

Why do the want the option?

And on the same note, are there any versions of Grep in widespread usage 
that don't support '--null'? AFAICT this flag was added to GNU Grep 2.4 
which was released in 1999.

> +(defconst grep--regexp-alist-bin-matcher
> +  '("^Binary file \\(.+\\) matches$" 1 nil nil 0 1))
> +(defconst grep-with-null-regexp-alist
> +  `(("^\\([^\0]+\\)\\(\0\\)\\([0-9]+\\):" 1 3 ,grep--regexp-alist-column nil nil

Any reason to change 2 to 3? Why don't we use a non-capturing group for 
\0 here?

If the numbers are the same, we could keep the variable's name the same 
as well. As a result, most third-party code would continue to simply work.

> +     (2 '(face unspecified display ":")))
> +    ,grep--regexp-alist-bin-matcher)
> +  "Regexp used to match grep hits.
> +See `compilation-error-regexp-alist'.")
> +(defconst grep-fallback-regexp-alist

Compensating for the multitude of variables by eliminating newlines 
between them doesn't look too hot to me.