Congrats on the 1.0, this is awesome! I love GitUp, and the source code looks clean as well. Some pointers to the good bits:
https://twitter.com/GitUpApp/status/633822376568852481
The downside is that the project is now in "scratch my own itch" mode:
https://twitter.com/GitUpApp/status/633821906387406848
So this is not going to be a commercial Tower.app killer (sadly, they deserve it :P - data corrupting bugs aren't being fixed etc. - but I guess SourceTree being free doesn't help the market.)