TypeError: findoutgoing() got an unexpected keyword argument 'heads'

Ubuntu から Mercurial で push しようとしたら、以下のエラーが出ました。

$ hg push
ssh://hg@bitbucket.org/codeigniter_jp/ci-ja への反映中
変更点を探索中
** 予期せぬ例外が浮揚されました。
**  http://mercurial.selenic.com/wiki/BugTracker まで
**  以下の情報を報告してください。
** Python 2.7.1+ (r271:86832, Apr 11 2011, 18:05:24) [GCC 4.5.2]
** Mercurial Distributed SCM (version 1.7.5)
** Extensions loaded: convert, graphlog, transplant, rebase, bookmarks, mq, git, color, extdiff, hgsubversion, histedit
Traceback (most recent call last):
  File "/usr/bin/hg", line 38, in <module>
    mercurial.dispatch.run()
  File "/usr/lib/pymodules/python2.7/mercurial/dispatch.py", line 16, in run
    sys.exit(dispatch(sys.argv[1:]))
  File "/usr/lib/pymodules/python2.7/mercurial/dispatch.py", line 36, in dispatch
    return _runcatch(u, args)
  File "/usr/lib/pymodules/python2.7/mercurial/dispatch.py", line 58, in _runcatch
    return _dispatch(ui, args)
  File "/usr/lib/pymodules/python2.7/mercurial/dispatch.py", line 593, in _dispatch
    cmdpats, cmdoptions)
  File "/usr/lib/pymodules/python2.7/mercurial/dispatch.py", line 401, in runcommand
    ret = _runcommand(ui, options, cmd, d)
  File "/usr/lib/pymodules/python2.7/mercurial/extensions.py", line 175, in wrap
    return wrapper(origfn, *args, **kwargs)
  File "/usr/lib/pymodules/python2.7/hgext/color.py", line 223, in colorcmd
    return orig(ui_, opts, cmd, cmdfunc)
  File "/usr/lib/pymodules/python2.7/mercurial/dispatch.py", line 644, in _runcommand
    return checkargs()
  File "/usr/lib/pymodules/python2.7/mercurial/dispatch.py", line 598, in checkargs
    return cmdfunc()
  File "/usr/lib/pymodules/python2.7/mercurial/dispatch.py", line 591, in <lambda>
    d = lambda: util.checksignature(func)(ui, *args, **cmdoptions)
  File "/usr/lib/pymodules/python2.7/mercurial/util.py", line 426, in check
    return func(*args, **kwargs)
  File "/usr/lib/pymodules/python2.7/mercurial/extensions.py", line 130, in wrap
    util.checksignature(origfn), *args, **kwargs)
  File "/usr/lib/pymodules/python2.7/mercurial/util.py", line 426, in check
    return func(*args, **kwargs)
  File "/home/kenji/bin/hgsubversion/hgsubversion/wrappers.py", line 489, in generic
    return orig(ui, repo, *args, **opts)
  File "/usr/lib/pymodules/python2.7/mercurial/util.py", line 426, in check
    return func(*args, **kwargs)
  File "/usr/lib/pymodules/python2.7/mercurial/extensions.py", line 130, in wrap
    util.checksignature(origfn), *args, **kwargs)
  File "/usr/lib/pymodules/python2.7/mercurial/util.py", line 426, in check
    return func(*args, **kwargs)
  File "/usr/lib/pymodules/python2.7/hgext/mq.py", line 2988, in mqcommand
    return orig(ui, repo, *args, **kwargs)
  File "/usr/lib/pymodules/python2.7/mercurial/util.py", line 426, in check
    return func(*args, **kwargs)
  File "/usr/lib/pymodules/python2.7/mercurial/extensions.py", line 130, in wrap
    util.checksignature(origfn), *args, **kwargs)
  File "/usr/lib/pymodules/python2.7/mercurial/util.py", line 426, in check
    return func(*args, **kwargs)
  File "/usr/lib/pymodules/python2.7/hgext/bookmarks.py", line 451, in push
    result = oldpush(ui, repo, dest, **opts)
  File "/usr/lib/pymodules/python2.7/mercurial/util.py", line 426, in check
    return func(*args, **kwargs)
  File "/usr/lib/pymodules/python2.7/mercurial/commands.py", line 2855, in push
    newbranch=opts.get('new_branch'))
  File "/home/kenji/bin/hgsubversion/hgsubversion/svnrepo.py", line 50, in wrapper
    return original(*args, **opts)
  File "/usr/lib/pymodules/python2.7/hgext/git/hgrepo.py", line 23, in push
    newbranch=newbranch)
  File "/usr/lib/pymodules/python2.7/hgext/mq.py", line 2892, in push
    return super(mqrepo, self).push(remote, force, revs, newbranch)
  File "/usr/lib/pymodules/python2.7/hgext/bookmarks.py", line 339, in push
    newbranch)
  File "/usr/lib/pymodules/python2.7/mercurial/localrepo.py", line 1320, in push
    ret = discovery.prepush(self, remote, force, revs, newbranch)
  File "/usr/lib/pymodules/python2.7/mercurial/discovery.py", line 208, in prepush
    update = findoutgoing(repo, remote, common, remoteheads)
  File "/usr/lib/pymodules/python2.7/mercurial/extensions.py", line 175, in wrap
    return wrapper(origfn, *args, **kwargs)
  File "/home/kenji/bin/hgsubversion/hgsubversion/__init__.py", line 102, in findoutgoing
    return orig(*args, **opts)
  File "/usr/lib/pymodules/python2.7/mercurial/extensions.py", line 175, in wrap
    return wrapper(origfn, *args, **kwargs)
  File "/usr/lib/pymodules/python2.7/hgext/git/__init__.py", line 115, in findoutgoing
    return orig(local, remote, base=base, heads=heads, force=force)
TypeError: findoutgoing() got an unexpected keyword argument 'heads'

調べると、hg-git のバグという情報がありましたので、~/.hgrc から「git =」をコメントアウトしたら解消しました。