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 11:33:08 +0100
> 
> > Thanks, this is fine, except that please use \\[quoted-insert] instead
> > of a literal \C-q, to DTRT when quoted-insert is rebound to some other
> > key.
> 
> Attached. I fixed my laziness about 'e.g.' for good measure.

Thanks, pushed.

> I'm hoping this can make emacs-26.

Documentation changes are always okay for the release branch.