If you have an empty repository (git init in an empty folder), then add files through GitPython, the repository isn't registered as "dirty" and diffs come back empty. For example:

>>> r = Repo('.')>>> r.index.add(["README"])>>> r.is_dirtyFalse>>> r.index.diff(None)[]

The index.entries property shows the newly added file, but there doesn't seem to be a way to turn it into "this file has been added, but not committed".