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

hg init
python -c 'print "confuse str.splitlines\nembedded\rnewline"' > a
hg ci -Ama -d '1 0'
echo clean diff >> a
hg ci -mb -d '2 0'
hg diff -r0 -r1