Document that git-log takes --all-match.

Signed-off-by: Mikael Magnusson <mikachu@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/rev-list-options.txt

@@ -174,6 +174,10 @@ endif::git-rev-list[]
 	Limit the commits output to ones with log message that
 	matches the specified pattern (regular expression).
 
+--all-match::
+	Limit the commits output to ones that match all given --grep,
+	--author and --committer instead of ones that match at least one.
+
 -i::
 --regexp-ignore-case::