Sorry, I keep that whole plugin as part of my dotfile repo. When the plugin upgrades itself, I just commit that upgrade. When I install my dotfile repo on a new machine, I have a script that symlinks everything to the repo, including my ST2 data. I then have my .gitignore set up to ignore all the plugins that get installed, but specifically track changes to the package manager plugin, as well as any other custom plugins I write for myself.
My bash-fu isn't great, can you point me at an example of a script which does this (yours or someone else's)? I was literally thinking about moving my ST2 config into my dotfiles repo the other day