- Start separating a "standalone" CLI. This is a little awkward with clap-
derive, but I got it working. Detection of whether the CLI _is_
standalone is still todo.
- Remove the old ad-hoc update code for code-server, and use the update
service instead.
- Fix some of the "permission denied" errors people got while updating
before. We need to rename the old running binary, not just overwrite it.