I haven't audited the rev-parse users, but I am having a feeling
that many of them would choke when they expect a couple of SHA1
object names and malicious user feeds them "--max-count=6" or
somesuch to shoot himself in the foot. Anyway, this adds a
couple of missing parameters that affect the list of revs to be
returned from rev-list, not the flags that affect how they are
presented by rev-list. I think that is the intention, but I am
not quite sure.