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

[Eli Zaretskii]

> From: Robert Pluim <rpluim@gmail.com>
> Date: Wed, 15 Nov 2017 10:58:19 +0100
> Cc: 29303@debbugs.gnu.org
> 
> diff --git a/lisp/vc/vc-git.el b/lisp/vc/vc-git.el
> index ed85603f82..fd5f5d5b63 100644
> --- a/lisp/vc/vc-git.el
> +++ b/lisp/vc/vc-git.el
> @@ -1428,7 +1428,8 @@ vc-git-grep
>                                  nil nil 'grep-history)
>            nil))
>        (t (let* ((regexp (grep-read-regexp))
> -             (files (grep-read-files regexp))
> +             (files (concat "'" (replace-regexp-in-string " " "' '"
> +                                (grep-read-files regexp)) "'"))
>               (dir (read-directory-name "In directory: "
>                                         nil default-directory t)))
>          (list regexp files dir))))))

This cannot be right, because this style of quoting only works with
Posix shells.