config: mark unused callback parameters

The callback passed to git_config() must conform to a particular
interface. But most callbacks don't actually look at the extra "void
*data" parameter. Let's mark the unused parameters to make
-Wunused-parameter happy.

Note there's one unusual case here in get_remote_default() where we
actually ignore the "value" parameter. That's because it's only checking
whether the option is found at all, and not parsing its value.

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

diff.c

@@ -264,7 +264,8 @@ void init_diff_ui_defaults(void)
 	diff_detect_rename_default = DIFF_DETECT_RENAME;
 }
 
-int git_diff_heuristic_config(const char *var, const char *value, void *cb)
+int git_diff_heuristic_config(const char *var, const char *value,
+			      void *UNUSED(cb))
 {
 	if (!strcmp(var, "diff.indentheuristic"))
 		diff_indent_heuristic = git_config_bool(var, value);