hashmap: mark unused callback parameters

Hashmap comparison functions must conform to a particular callback
interface, but many don't use all of their parameters. Especially the
void cmp_data pointer, but some do not use keydata either (because they
can easily form a full struct to pass when doing lookups). Let's mark
these to make -Wunused-parameter happy.

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

environment.c

@@ -333,10 +333,10 @@ static void set_git_dir_1(const char *path)
 	setup_git_env(path);
 }
 
-static void update_relative_gitdir(const char *name,
+static void update_relative_gitdir(const char *UNUSED(name),
 				   const char *old_cwd,
 				   const char *new_cwd,
-				   void *data)
+				   void *UNUSED(data))
 {
 	char *path = reparent_relative_path(old_cwd, new_cwd, get_git_dir());
 	struct tmp_objdir *tmp_objdir = tmp_objdir_unapply_primary_odb();