refs: mark unused each_ref_fn parameters

Functions used with for_each_ref(), etc, need to conform to the
each_ref_fn interface. But most of them don't need every parameter;
let's annotate the unused ones to quiet -Wunused-parameter.

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

reflog.c

@@ -294,7 +294,8 @@ int should_expire_reflog_ent_verbose(struct object_id *ooid,
 	return expire;
 }
 
-static int push_tip_to_list(const char *refname, const struct object_id *oid,
+static int push_tip_to_list(const char *UNUSED(refname),
+			    const struct object_id *oid,
 			    int flags, void *cb_data)
 {
 	struct commit_list **list = cb_data;