Document 'git-log --decorate'

Signed-off-by: Michael Hendricks <michael@ndrix.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
diff --git a/Documentation/git-log.txt b/Documentation/git-log.txt
index 49bb539..dd06527 100644
--- a/Documentation/git-log.txt
+++ b/Documentation/git-log.txt
@@ -51,6 +51,9 @@
 	a record about how the tip of a reference was changed.
 	See also gitlink:git-reflog[1].
 
+--decorate::
+    Print out the ref names of any commits that are shown.
+
 <paths>...::
 	Show only commits that affect the specified paths.