rev-list split: minimum fixup.

rev-list split: minimum fixup.

This fixes "the other end has commit X but since then we tagged
that commit with tag T, and he says he wants T -- what is the
list of objects we need to send him?" question:

	git-rev-list --objects ^X T

We ended up sending everything since the beginning of time X-<.

Signed-off-by: Junio C Hamano <junkio@cox.net>