miniblog.

I'm experimenting with jj this weekend. It seems pretty nice so far, but the mental model is pretty different from git. For example, there's no `checkout` command. You do `jj new ABC` to switch to a commit, which creates a new empty commit on top of ABC.

What exactly is a subtype? I've gone through a whole range of mental models as I've learnt about type systems. How do you think about them?

Persisting editor and mental state across debugging sessions is really hard. It's often easier to have a single, longer debugging session.