Add revlog.parentrevs function.
This allows one to walk the revision graph using only revision numbers,
which can be faster than using revision hashes, especially for
RevlogNG, where the parents of a revision are stored as revision
numbers.
#!/bin/sh
hg init 1
echo '[ui]' >> 1/.hg/hgrc
echo 'timeout = 10' >> 1/.hg/hgrc
echo foo > 1/foo
hg --cwd 1 ci -A -m foo
hg clone 1 2
hg clone 2 3
echo '[hooks]' >> 2/.hg/hgrc
echo 'changegroup.push = hg push -qf ../1' >> 2/.hg/hgrc
echo bar >> 3/foo
hg --cwd 3 ci -m bar
hg --cwd 3 push ../2