I love this! As somebody who quite frequently performs pair programming, this is a great feature. I’ve always found it unfair when only one of the two people got to “keep their streak up”, I mean, it’s a group effort after all!
It doesn't work great for our open source projects though where visibility on GitHub tends to be more important.
I think that `how much code has been changed by developer` is not a good metric for performance. There might be weeks when I'm barely writing any code and getting the most work done.
Issue trackers on the other hand can be good to track performance.