git

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