revset: optimized _revancestors method based on order of revisions
If the revisions for which the ancestors are required are in descending order,
it lazily loads them into a heap to be able to yield values faster.
$ echo "[extensions]" >> $HGRCPATH
$ echo "mq=" >> $HGRCPATH
$ hg init
$ echo 'base' > base
$ hg ci -Ambase
adding base
$ hg qnew -mmqbase mqbase
$ hg qsave
$ hg qrestore 2
restoring status: hg patches saved state