To update to the latest development source, run the commands below, where SAGE_ROOT is the root directory of the Sage installation, and where hackdir is a directory you create for working on code changes (it need not have the name or location given below).
This will create a new sagenb repository ignoring any changes you have made to the files.
mkdir ~/hackdir cd ~/hackdir git clone git://github.com/sagemath/sagenb.git sagenb-git cd SAGE_ROOT/devel rm sagenb ln -s ~/hackdir/sagenb sagenb cd sagenb ../../sage setup.py develop
What this has done is to create a new directory, move to that directory, and create a clone of the most up-to-date version of the upstream notebook sources there. Then we remove a symbolic link sagenb in the Sage folder and replace it with a link to your clone of upstream, finally making sure that the notebook has the correct dependencies.
An advantage of having the separate directory for sagenb is that you would later be able to keep it and do development work in it even when you upgrade Sage, or even if you accidentally destroy your Sage installation somehow.
The rest of these instructions is some very generic documentation, slightly adapted to help develop the notebook using Git and Github.
The most important section involves how to update your new sagenb source repository and create a “fork” of the master copy, so that you will be able to request your changes to be merged in the Sage notebook, called a “pull request”; see Git for Development.