Be aware this is a preview. Don't merge this into your main branch and run along using it. I've tested it a lot but there may be issues I'm unaware of. Create a test branch for your blog before you continue. When everything gets cleared up, I'll release this feature and you can pull from the master branch.
First be sure you have a remote pointing to the Octopress repository. git remote -v
should return something like this:
octopress git://github.com/imathis/octopress.git (fetch)