This changes the revlog.group and re-implements the localrepo.changeroup
function in terms of it.
revlog.group now takes a list of nodes, and some callback functions
instead of a linkmap.
# 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