Yes - easily able to do a diff with previous versions will be of great value when creating a story. Its in the feature list backlog. Will get on it soon.
private repo is in the works. Will be available as an app in github marketplace. Bitbuket and gitlab support coming soon. You can sign up to be notified here.
Current plan is to make this available for free to public repos. Will be adding an app in github marketplace for private repos. Code will be open sourced after some cleanup.