tests/helper-runtests.sh

revset: do not rewrite ':y' to '0:y' (issue5385)

That's no longer valid since the revision 0 may be hidden. Bypass validating
the existence of '0' and filter it by spanset.

#
# Avoid interference from actual test env:

unset HGTEST_JOBS
unset HGTEST_TIMEOUT
unset HGTEST_PORT
unset HGTEST_SHELL