restructure changelog file appending - make appending code proper part of changelog with delayupdate/finalize - use simplified appender that tracks pending data in memory - eliminate old appendfile and helper classes - update addchangegroup to use new interface and reuse the existing changelog

#!/bin/sh

mkdir t
cd t
hg init
echo a > a
hg add a
hg commit -m "test" -d "1000000 0"
hg verify
hg parents
hg status
hg rollback
hg verify
hg parents
hg status