Hello Guix!

Today I added support for “one-shot” services in the Shepherd:

  https://git.savannah.gnu.org/cgit/shepherd.git/commit/?id=c121eedfff7a50feddcf08e173d2b0dd807e8804

One-shot services start, perform a short action, and are immediately
marked as “stopped.”  (systemd has something similar:
<https://www.freedesktop.org/software/systemd/man/systemd.service.html>.)

The use case is initialization or cleanup actions like the ‘user-homes’
service.  So far ‘user-homes’ is a regular service whose ‘start’ method
always fails; as a result, we always see this message:

  Service user-homes could not be started.

From there on, we’ll be able to mark this service as one-shot (patch
below), and thus shepherd will notice that it successfully started (or
not) and yet mark it as stopped, which was always the intent.

There are other cases where this could be useful.  For instance, we
could turn service activation snippets into one-shot services.

Since this augments the Shepherd API, I plan to release it as 0.6.0
in time for Guix 1.0.  It contains other rather minor changes compared
to 0.5.0.

Feedback welcome!

Ludo’.