git clone git@github.com:USERNAME/FORKED-REPO.git
cd into/cloned/fork-repo
git remote add upstream git://github.com/ORIGINAL-USERNAME/ORIGINAL-REPO.git
git fetch upstream
git pull upstream master
git clone git@github.com:USERNAME/FORKED-REPO.git
cd into/cloned/fork-repo
git remote add upstream git://github.com/ORIGINAL-USERNAME/ORIGINAL-REPO.git
git fetch upstream
git pull upstream master