Avoid misleading success message on error

When a push fails (for example when the remote head does not fast forward
to the desired ref) it is not correct to print "Everything up-to-date".

Signed-off-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>
diff --git a/send-pack.c b/send-pack.c
index a41bbe5..5bc2f01 100644
--- a/send-pack.c
+++ b/send-pack.c
@@ -272,7 +272,7 @@
 	packet_flush(out);
 	if (new_refs)
 		pack_objects(out, remote_refs);
-	else
+	else if (ret == 0)
 		fprintf(stderr, "Everything up-to-date\n");
 	close(out);
 	return ret;