test: add an extra base changeset in test-obsolete.t...
test: add an extra base changeset in test-obsolete.t
A fix to issue4982 (not fixed in this patch) will reinforce the filtering
during discovery. This will makes two of our test repositories appear
unrelated (because all common content is properly hidden). To avoid this, we
introduce an extra base changeset that will not get obsoleted. This affects
various test output so we put this addition in its own changeset.