bash autocompletion for sontrib/subtree?

I've built/installed git from src,

 git --version
  git version 1.9.rc2.15.g89ba81d

& installed/sourced 

 /etc/bash_completion.d/git-completion.bash

For all git-core builtins, autocompletion works.

I've also installed contrib/subtree

`git subtree` works, but I get no autocompletion for the command.

I've tried adding/sourcing this script (@ https://github.com/camptocamp/puppet-git-subtree/blob/master/files/bash_completion.sh),

------------------------- _git_subtree () { local cur="${COMP_WORDS[COMP_CWORD]}"

if [ $COMP_CWORD -eq 2 ]; then __gitcomp "add merge pull push split" return elif [ $COMP_CWORD -eq 3 ]; then __gitcomp "--prefix=" return fi __gitcomp "$(__git_remotes)" } -------------------------

but still get not subtree autocomplete.

What's neede to enable subtree's autocomplete?