tests/test-conflict.out

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

merge: warning: conflicts during merge
merging a
merging a failed!
e7fe8eb3e180+0d24b7662d3e+ tip
something else
=======
something
M a