GIT is a version controlling system used in software engineering. For Data Scientists working in teams, I recommend using it for especially for your python code. Though you can check-in Jupiter notebooks, GIT is not very helpful for collaborating with Jupyter notebooks — in fact, I am not aware of any better collaborative environments for Jupyter notebooks. Please leave a comment if something works for you.
With GIT, it is easy to find common commands to perform certain actions. But when mistakes happen (mistakes do happen), it is hard to find how to undo what you just did. This is page serves as a reference on how to undo common tasks on GIT.