bug#29303: 25.2; vc-git-grep should shell-escape FILES

[Eli Zaretskii]

> From: Robert Pluim <rpluim@gmail.com>
> Cc: 29303@debbugs.gnu.org,  gus@inodes.org
> Date: Fri, 17 Nov 2017 09:38:33 +0100
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> >> From: Robert Pluim <rpluim@gmail.com>
> >> That's a good question. Note that interactively entering patterns with
> >> a space is currently a pain, since grep-read-files uses
> >> read-file-name-internal, which attempts to do completion if you type
> >> <SPC>. So this would presumably only affect people who have changed
> >> grep-files-aliases and have patterns with embedded whitespace.
> >
> > Maybe we should mention this in the doc string
> 
> For vc-git-grep, or for every function that uses grep-read-files?

The latter, I think.  If there are too many of those callers, then we
could describe this once, say in grep-read-files, and then reference
that, with something like

  Including whitespace in the pattern requires quoting, see
  `grep-read-files' for the details.

Thanks.