The remote-helper bridges to access data stored in Mercurial and
Bazaar are maintained outside the git.git tree in the repositories
of their primary author:

    https://github.com/felipec/git-remote-hg (for Mercurial)
    https://github.com/felipec/git-remote-bzr (for Bazaar)

You can pick a directory on your $PATH and download them from these
repositories, e.g.:

  $ wget -O $HOME/bin/git-remote-hg \
    https://raw.github.com/felipec/git-remote-hg/master/git-remote-hg
  $ wget -O $HOME/bin/git-remote-bzr \
    https://raw.github.com/felipec/git-remote-bzr/master/git-remote-bzr
  $ chmod +x $HOME/bin/git-remote-hg $HOME/bin/git-remote-bzr