doc: use linkgit macro where needed.

Signed-off-by: Jean-Noël Avila <jn.avila@free.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/Documentation/git-grep.txt b/Documentation/git-grep.txt
index a7f9bc9..6077ff0 100644
--- a/Documentation/git-grep.txt
+++ b/Documentation/git-grep.txt
@@ -209,7 +209,7 @@
 	Use \0 as the delimiter for pathnames in the output, and print
 	them verbatim. Without this option, pathnames with "unusual"
 	characters are quoted as explained for the configuration
-	variable core.quotePath (see git-config(1)).
+	variable core.quotePath (see linkgit:git-config[1]).
 
 -o::
 --only-matching::