test-copies: introduce case combining the `p` and `q` branch
That case involves conflicting copies information from each branch. It is
similar to the `mAEm` / `mEAm` case except this case actual content merge is
involved too.
Differential Revision: https://phab.mercurial-scm.org/D10057
#
# Avoid interference from actual test env:
unset HGTEST_JOBS
unset HGTEST_TIMEOUT
unset HGTEST_PORT
unset HGTEST_SHELL