This information comes from a post by @dblockdotorg which was down today while I was trying to set my blog up on a fresh OS install. Therefore, I’m mirroring that content here in case it is unavailable in the future.

$ git clone git@github.com:username/username.github.com.git
$ cd username.github.com
$ git checkout source
$ mkdir _deploy
$ cd _deploy
$ git init
$ git remote add origin git@github.com:username/username.github.com.git
$ git pull origin master
$ cd ..