Make "checkout-cache" silently skip up-to-date files.

It used to always overwrite them if forced. Now it just
realizes that they are already ok, and don't need to be
touched.

checkout-cache.c

@@ -96,12 +96,14 @@ static int write_entry(struct cache_entry *ce)
 
 static int checkout_entry(struct cache_entry *ce)
 {
-	if (!force) {
 	struct stat st;
 
 	if (!stat(ce->name, &st)) {
 		unsigned changed = cache_match_stat(ce, &st);
-			if (changed && !quiet)
+		if (!changed)
+			return 0;
+		if (!force) {
+			if (!quiet)
 				fprintf(stderr, "checkout-cache: %s already exists\n", ce->name);
 			return 0;
 		}