I use git to update my copy of a project when new features are added. Git provides a very nice summary of the changes that have been made, something like this:
intro/matplotlib/matplotlib.rst                             |  266 +++--
intro/numpy/advanced_operations.rst                         |   62 +-
intro/numpy/array_object.rst                                |  630 ++++++----
With this I can also follow the development of the project and it is quite useful.
At some point I made some personal changes to the source code of the project, but then I reverted it.
Since then, I think, the nice summary disappeared, and instead this line is shown each time I do git pull:
First, rewinding head to replay your work on top of it...
How to revert things and make the summary appear again?
 
    