builtin-log.c: Fix typo in comment

s/fmt-patch/format-patch/

Signed-off-by: Frank Lichtenheld <frank@lichtenheld.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>

builtin-log.c

@@ -439,7 +439,7 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 
 	/*
 	 * Parse the arguments before setup_revisions(), or something
-	 * like "git fmt-patch -o a123 HEAD^.." may fail; a123 is
+	 * like "git format-patch -o a123 HEAD^.." may fail; a123 is
 	 * possibly a valid SHA1.
 	 */
 	for (i = 1, j = 1; i < argc; i++) {