Improve progress bar reporting

[guyzmo]

Currently progress bar is not really reporting progress (it's appearing at the end already at 100%). Something's wrong in the implementation between GitPython and my code, need to be investigated.

[guyzmo]

cf gitpython-developers/GitPython#444

[guyzmo]

Ok, issue fixed in upstream, need to wait for new release:

• http://asciinema.org/a/5n0tyv6jmvu14u8lsi18f53c5