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

# Test for changeset ba7c74081861
# (update dirstate correctly for non-branchmerge updates)
hg init a
cd a
echo a > a
hg add a
hg commit -m a
cd ..
hg clone a b
cd a
hg mv a b
hg commit -m move
echo b >> b
hg commit -m b
cd ../b
hg pull ../a
hg update