Go into the folder.. If the folder is empty, then:
git clone git@github.com:whatever .
else
git init
git remote add origin PATH/TO/REPO
git fetch
git checkout -t origin/master
Go into the folder.. If the folder is empty, then:
git clone git@github.com:whatever .
else
git init
git remote add origin PATH/TO/REPO
git fetch
git checkout -t origin/master