This is the Git repository used to store some on-going work by CGAL developers. The repository that hosts the master branch of CGAL is CGAL/cgal.
To start working with this repository, you must also set the a remote repository that contains the master branch of CGAL:
git remote add cgal git@github.com:CGAL/cgal.git
Then you can create your own working branch. Say, your name is rineau and you will work on a new read/write function for the Triangulation package:
git checkout -b Triangulation-add_input_output-rineau --no-track cgal/master
More details on the developement of new features can be found on the CGAL wiki.