add --plain option to patchbomb.
this omits the hg patch headers. it makes a patchbomb email look like
a regular email with a patch.
# repo.py - repository base classes for mercurial
#
# Copyright 2005 Matt Mackall <mpm@selenic.com>
#
# This software may be used and distributed according to the terms
# of the GNU General Public License, incorporated herein by reference.
class RepoError(Exception): pass