revlog: do inclusive descendant testing (API)
In many other places, a revision is considered a descendant of itself. We
update the behavior of `revlog.descendant()` to match this. (for example.
`revlog.isancestor` does inclusive testing).
No tests break, so it seems safe to do so.
This will make it easier to use a more efficient implementation in a later
changeset.
pager.pager=p0 # $TESTTMP/sysrc:4
ui.editor=e1 # $TESTTMP/userrc:2
pager.pager=p2 # $PAGER
ui.editor=e1 # $TESTTMP/userrc:2