If we update the 'old' node, we might be updating the remote bookmark
even when our 'new' node is not related at all to what the remote has,
effectively forcing an update.
Let's do that only when forced push is configured.
Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>