new extension: fetch -> combine pull and merge/update pull changes from remote repo. if changes add new head: merge with new head, commit result. else: update working dir to new head. this makes useful command like git 'pull' command.

#!/bin/sh

hg init
mkfifo p

hg serve --stdio < p &
P=$!
(echo lock; echo addchangegroup; sleep 5) > p &
Q=$!
sleep 3
kill -HUP $P
wait
ls .hg