Jan Engelhardt noticed that while --topo-order can be overridden by a
subsequent --date-order, the reverse was not possible. That's because
setup_revisions() failed to set revs->lifo properly.
Signed-off-by: Michele Ballabio <barra_cuda@katamail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>