tests/helper-runtests.sh

revlog: refactor out the rev-oriented part of commonancestorheads

We plan to use this in a function taking revs as argument. Round trips to nodes
seem silly.

#
# Avoid interference from actual test env:

unset HGTEST_JOBS
unset HGTEST_TIMEOUT
unset HGTEST_PORT
unset HGTEST_SHELL