Force editor to appear for an 'hg backout' if a message or logfile aren't
supplied. Pre-fill the commit message with the changeset being backed out.
Fixes bug 238.
# 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