tests/test-push-hook-lock

support hooks written in python.

to write hook in python, create module with hook function inside.
make sure mercurial can import module (put it in $PYTHONPATH or load it
as extension).  hook function should look like this:

def myhook(ui, repo, hooktype, **kwargs):
   if hook_passes:
      return True
   elif hook_explicitly_fails:
      return False
   elif some_other_failure:
      import util
      raise util.Abort('helpful failure message')
   else:
      return
      # implicit return of None makes hook fail!

then in .hgrc, add hook with "python:" prefix:

[hooks]
commit = python:mymodule.myhook

#!/bin/sh
hg init 1
echo '[ui]' >> 1/.hg/hgrc
echo 'timeout = 10' >> 1/.hg/hgrc
echo foo > 1/foo
hg --cwd 1 ci -A -m foo
hg clone 1 2
hg clone 2 3
echo '[hooks]' >> 2/.hg/hgrc
echo 'changegroup.push = hg push -qf ../1' >> 2/.hg/hgrc
echo bar >> 3/foo
hg --cwd 3 ci -m bar
hg --cwd 3 push ../2