Right now Sourcetree only seems to save what windows are open when the application is properly shut down with Cmd-Q. If Sourcetree crashes, or is killed (for example system shutdown), you will not be returned to the same state.

I think it would be very useful (and likely very simple to implement) to make sure Sourcetree saves what windows are open as soon as they change, so it can restore its state no matter how it was shut down.