tests/helper-runtests.sh

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.

#
# Avoid interference from actual test env:

unset HGTEST_JOBS
unset HGTEST_TIMEOUT
unset HGTEST_PORT
unset HGTEST_SHELL