In order to further deduplicate the contents of the various unit
files, we need to be able to merge multiple additional units
into the initial one.
Luckily the merge logic is in no way constrained to working with
just two units, so achieving this is pretty much just a matter
of lifting the existing limitation on the number of arguments
that the script accepts.
As a special case, it's now also possible to call the script
with just the base unit as argument. No merging will be performed
in that case, obviously, but we'll still go through the basic
validation and cleanup steps.
This also fixes a bug in the check for the number of arguments:
sys.argv also contains the name of the script, so we should have
checked that its size was at least 3. The check is now written in
a way that's less prone to misunderstandings.
Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
We already use templating to generate sockets, which are all
based off libvirtd's. Push the idea further, and extend it to
cover services as well.
This is more challenging, as the various modular daemons each have
their own needs in terms of what system services needs to be
available before they can be started, which other components of
libvirt they depend on, and so on.
In order to make this sort of per-service tweaks possible, we
introduce a Python script that can merge two systemd units
together. The script is aware of the semantics of systemd's unit
definition format, so it can intelligently merge sections
together.
This generic systemd unit merging mechanism will also supersede
the extremely ad-hoc @deps@ variable, which is currently used in
a single scenario.
Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
