add prechangegroup and pretxnchangegroup hooks. prechangegroup lets you stop push, pull or unbundle before it begins. pretxnchangegroup lets you inspect changegroup before transaction is committed, and roll back if you not like it.

#!/bin/sh

hg
hg -q
hg help
hg -q help
hg add -h
hg add --skjdfks
hg help diff
hg help status
hg -q help status
hg help foo
hg skjdfks

exit 0