pupistry diff is too noisy

[jethrocarr]

pupistry diff is too noisy when doing branches, since any change visible in multiple branches gets diffed multiple times. Additionally, creating a new branch creates an initial mega-diff of what has changed.

The diff function needs to be a lot smarter in order to scale beyond small users. This ticket is a reminder to self to fix, or an invitation for a pull request from you, the wonderful reader of this issue whom would like to fix it for all. :-)