Remove unconnected outlets and code that references them.
Break retain cycle by making back-reference to parent weak.
Break cycles by making back-references to PBGitRepository weak
Make reference from view controller back to window controller weak, breaks cycle.
Remove unused ivar.
Break retain cycles for PBGitCommitController and related classes.
Break retain cycles for the PBGitHistoryController and related classes.
Broke last retain cycle and now finally the PBGitRepository gets dealloced when the window gets closed.
Break the PBGitHistoryList/PBGitHistoryGrapher cycle. I wonder what made me think the last one was the last...
Remove yet another cycle. That should be the last one now, at least for the history part.
Wrap an autorelease pool around walkRevisionListWithSpecifier:
Fix leaks of PBGitLane. 

In my testing currentLane always was leaked at this point. But I am not sure if there might be some cases where the PBGitLane at this point is referenced from somewhere else.