R1:118c696f727a

Separate repository updates from the pull daemon

Summary:
Ref T4605. Currently, the PullLocal daemon is responsible for two relatively distinct things:

- scheduling repository updates; and
- actually updating repositories.

Move the "actually updating" part into a new `bin/repository update` command, which basically runs the pull, discover, refs and mirror commands. This will let the parent process focus on scheduling in a more understandable way and update multiple repositories at once. It also…