bug#8684: The fix introduce another bug

[Stefan Monnier]

> When type enter key in *grep* buffer, the following message will showed.
> compilation-next-error: No grep hit here.
> If I revert the change, the message disappears.

I've installed the patch below which should hopefully fix the original
problem as well as the new one.


        Stefan


=== modified file 'lisp/ChangeLog'
--- lisp/ChangeLog      2011-05-21 22:33:12 +0000
+++ lisp/ChangeLog      2011-05-21 23:17:35 +0000
@@ -1,3 +1,7 @@
+2011-05-21  Stefan Monnier  <monnier@iro.umontreal.ca>
+
+       * progmodes/grep.el (grep-mode): Fix last change (bug#8684).
+
 2011-05-21  Glenn Morris  <rgm@gnu.org>
 
        * files.el (hack-local-variables-prop-line, hack-local-variables):

=== modified file 'lisp/progmodes/grep.el'
--- lisp/progmodes/grep.el      2011-05-17 18:14:30 +0000
+++ lisp/progmodes/grep.el      2011-05-21 23:13:56 +0000
@@ -698,7 +698,9 @@
        grep-hit-face)
   (set (make-local-variable 'compilation-error-regexp-alist)
        grep-regexp-alist)
-  (set (make-local-variable 'compilation-directory-matcher) nil)
+  ;; compilation-directory-matcher can't be nil, so we set it to a regexp that
+  ;; can never match.
+  (set (make-local-variable 'compilation-directory-matcher) "\\`a\\`")
   (set (make-local-variable 'compilation-process-setup-function)
        'grep-process-setup)
   (set (make-local-variable 'compilation-disable-input) t)