remote-helpers: return successfully if everything up-to-date

Signed-off-by: Clemens Buchacher <drizzd@aon.at>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/transport-helper.c b/transport-helper.c
index 16c6641..5078c71 100644
--- a/transport-helper.c
+++ b/transport-helper.c
@@ -263,6 +263,8 @@
 		strbuf_addstr(&buf, ref->name);
 		strbuf_addch(&buf, '\n');
 	}
+	if (buf.len == 0)
+		return 0;
 
 	transport->verbose = flags & TRANSPORT_PUSH_VERBOSE ? 1 : 0;
 	standard_options(transport);