To follow the tutorial step by step just clone the repository from the master branch (which is empty) and then start merging in each exercise, ie:
$ git clone git://github.com/proofek/phpnw12-tutorial.git
$ cd phpnw12-tutorial.git
$ git pull origin exercise-1
$ git pull origin exercise-2
$ git pull origin exercise-3
See the commit messages that provide a walkthough guide for every step.
To quickly jump to a specific scenario, clone the repository from the master branch (which is empty) and then create a local branch for the specific exercise:
$ git clone git://github.com/proofek/phpnw12-tutorial.git
$ cd phpnw12-tutorial.git
$ git checkout -b exercise-1 origin/exercise-1
$ git checkout -b exercise-2 origin/exercise-2
$ git checkout -b exercise-3 origin/exercise-3
You can easily follow every step by just looking at the commit history on github by simply switching between branches from github's UI