Fixes for push corner case TAH found a bug where push would push things the remote already had, raising an assertion. This turned out to be because the changeset protocol was not recording a common subset node in one case. Also discovered was that the protocol was queueing multiple copies of a node for pull. Fixed by changing fetch to a hash. Add some more debugging output.

#!/bin/sh

hg init
mkfifo p

hg serve --stdio < p &
P=$!
(echo lock; echo addchangegroup; sleep 5) > p &
Q=$!
sleep 1
kill -HUP $P
sleep 1
ls .hg