Configure fancy git to show the number of changed/staged files

[henhal]

New user of fancy-git here and loving it.
However, before using fancy-git I used my homemade bash script to modify PS1 with some data from git. Specifically, my prompt would look a bit like this:

user@host /some/path (branch) (2 changed) (3 staged) $

I really do miss the possibility to see how many file I've just added to the index using git add -u, to avoid mistakes.
Is it possible to configure fancy-git to do this?
Or could I easily patch the prompt with my own additions? Is there a guide on how to add custom changes to the prompt?

Thanks!