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>

pretty.c

@@ -43,7 +43,8 @@ static void save_user_format(struct rev_info *rev, const char *cp, int is_tforma
 	rev->commit_format = CMIT_FMT_USERFORMAT;
 }
 
-static int git_pretty_formats_config(const char *var, const char *value, void *cb)
+static int git_pretty_formats_config(const char *var, const char *value,
+				     void *UNUSED(cb))
 {
 	struct cmt_fmt_map *commit_format = NULL;
 	const char *name;