read-cache: use oideq() in ce_compare functions

These functions return the full oidcmp() value, but the
callers really only care whether it is non-zero. We can use
the more strict !oideq(), which a compiler may be able to
optimize further.

This does change the meaning of the return value subtly, but
it's unlikely that anybody would try to use them for
ordering. They're static-local in this file, and they
already return other error values that would confuse an
ordering (e.g., open() failure gives -1).

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

read-cache.c

@@ -213,7 +213,7 @@ static int ce_compare_data(const struct cache_entry *ce, struct stat *st)
 	if (fd >= 0) {
 		struct object_id oid;
 		if (!index_fd(&oid, fd, st, OBJ_BLOB, ce->name, 0))
-			match = oidcmp(&oid, &ce->oid);
+			match = !oideq(&oid, &ce->oid);
 		/* index_fd() closed the file descriptor already */
 	}
 	return match;
@@ -254,7 +254,7 @@ static int ce_compare_gitlink(const struct cache_entry *ce)
 	 */
 	if (resolve_gitlink_ref(ce->name, "HEAD", &oid) < 0)
 		return 0;
-	return oidcmp(&oid, &ce->oid);
+	return !oideq(&oid, &ce->oid);
 }
 
 static int ce_modified_check_fs(const struct cache_entry *ce, struct stat *st)