The `runsvc.sh` script wraps a JavaScript script which starts
`Runner.Listener` and also handles failures. This has the downside that
the service _always_ exits with status code 0, i.e., success. This
causes frequent service restarts when running in ephemeral mode with a
faulty config as Systemd always sees a success exit status. To prevent
this, this commit changes the service config to call `Runner.Listener`
directly. The JavaScript wrapper stops the process with a SIGINT, hence,
the Systemd unit now sends a SIGINT to stop the service.
Adds the module option `ephemeral`. If set to true, configures the
runner registration with the `--ephemeral` option. This causes the
runner to exit after processing a single job, to de-register itself, and
to delete its configuration. Afterward, systemd restarts the service
which triggers a new ephemeral registration with a clean state.
This commit introduces support for runner registrations through a
personal access token (PAT). To use a PAT instead of a registration
token, place an appropriately scoped PAT in `tokenFile`. If the file
contains a PAT, the configuration script queries a new runner
registration token. Using a runner registration token directly continues
to work as before.
Using the runtime directory as `RUNNER_ROOT` is wrong. We should always
use the state directory like we already do when invoking the runner
configure script. Otherwise, the runner constructs the wrong path for
some files (.credentials, .runner, ...).
This was enabled by default in 18a7ce76fc
with the reason that it would be "useful regardless of the desktop
environment.", which I'm not arguing against.
The reason why this should not be enabled by default is that there are a
lot of systems that NixOS runs on that are not desktop systems.
Users on such systems most likely do not want or need this feature and
could even consider this an antifeature.
Furthermore, it is surprising to them to find out that they have this
enabled on their systems.
They might be even more surprised to find that they have polkit enabled
by default, which was a default that was flipped in
a813be071c. For some discussion as to why
see https://github.com/NixOS/nixpkgs/pull/156858.
Evidently, this default is not only surprising to users, but also module
developers, as most if not all modules for desktop environments already
explicity set services.udisks2.enable = true; which they don't need to
right now.
