prio-queue: mark unused parameters in comparison functions

The prio_queue_compare_fn interface has a void pointer to allow callers
to pass arbitrary data, but most comparison functions don't need it.
Mark those cases to make -Wunused-parameter happy.

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

commit.c

@@ -801,7 +801,8 @@ int compare_commits_by_author_date(const void *a_, const void *b_,
 	return 0;
 }
 
-int compare_commits_by_gen_then_commit_date(const void *a_, const void *b_, void *unused)
+int compare_commits_by_gen_then_commit_date(const void *a_, const void *b_,
+					    void *unused UNUSED)
 {
 	const struct commit *a = a_, *b = b_;
 	const timestamp_t generation_a = commit_graph_generation(a),
@@ -821,7 +822,8 @@ int compare_commits_by_gen_then_commit_date(const void *a_, const void *b_, void
 	return 0;
 }
 
-int compare_commits_by_commit_date(const void *a_, const void *b_, void *unused)
+int compare_commits_by_commit_date(const void *a_, const void *b_,
+				   void *unused UNUSED)
 {
 	const struct commit *a = a_, *b = b_;
 	/* newer commits with larger date first */

negotiator/skipping.c

@@ -50,7 +50,7 @@ struct data {
 	int non_common_revs;
 };
 
-static int compare(const void *a_, const void *b_, void *unused)
+static int compare(const void *a_, const void *b_, void *data UNUSED)
 {
 	const struct entry *a = a_;
 	const struct entry *b = b_;

t/helper/test-prio-queue.c

@@ -2,7 +2,7 @@
 #include "cache.h"
 #include "prio-queue.h"
 
-static int intcmp(const void *va, const void *vb, void *data)
+static int intcmp(const void *va, const void *vb, void *data UNUSED)
 {
 	const int *a = va, *b = vb;
 	return *a - *b;