shrink-revlog: add "reverse postorder" and "postorder reverse" toposorts.
Based on a patch by Benoit Boissinot, adapted to the pluggable sort
algorithm design. toposort_reversepostorder() is a very good
performer; it's designed to recreate what the revlog would have looked
like if Mercurial had parent deltas now. toposort_postorderreverse()
is unstable and very inconsistent, but perhaps with some work it could
be made better.
#!/bin/sh
rm -rf a
hg init a
cd a
echo a > a
hg ci -Am0
hg tag t1 # 1
hg tag --remove t1 # 2
hg co 1
hg tag -r0 t1
hg tags