ls-tree: mark unused parameter in callback

The formatting functions are dispatched from a table of function
pointers. The "path name only" function unsurprisingly does not need to
look at its "oid" parameter, but we must mark it as unused to make
-Wunused-parameter happy.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/ls-tree.c

@@ -241,7 +241,8 @@ static int show_tree_long(const struct object_id *oid, struct strbuf *base,
 	return recurse;
 }
 
-static int show_tree_name_only(const struct object_id *oid, struct strbuf *base,
+static int show_tree_name_only(const struct object_id *oid UNUSED,
+			       struct strbuf *base,
 			       const char *pathname, unsigned mode,
 			       void *context)
 {