Sometimes it's useful to be able to run synapse in the foreground for debugging. You can do this by running python -m synapse.app.homeserver directly, but that means you don't get quite the same environment as synctl gives you, and in any case it's opaque for users.

We should give synctl a --no-daemonize option, which makes it run synapse without the --daemonize option.

(It would be an error to try to set --no-daemonize and --all-processes at the same time)