The directed graph isn't the problem. I think people can deal with the idea that other people have a different version of the code from them. The parts that are hard are the horribly inconsistent commands and the complete mess that is how the staging area interacts with everything else.
The commands suffer from backwards compatibility. And at some point in git's development it was easier to get new options to existing commands approved than new commands. So that's eg the reason 'checkout' and 'reset' do lots of different things.
I wonder whether we could create a much better and more consistent command line interface from scratch?
