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
# http://www.selenic.com/mercurial/bts/issue433
hg init a
cd a
echo a > a
hg commit -Ama
hg parents -r 0 doesnotexist
true