Post #1991115

@spacebuffer Yeah, I did not expect this to work at all. I would have been satisfied if it was just tied to a null user or something and the issues became append-only. But it does work, and it's so wonderful. The PR migration is really clever too. Obviously the user that opened the PR doesn't have an account yet so it looks like the source branch gets attached to the target repository, but is hidden and isolated somehow (unless you explicitly click through to it), which is pretty much the best solution I can realistically imagine.