apply override_rc deterministically

[bugfood]

When applying conf.d overrides to enable restarts for services that already have matching entries in the default override_rc, we can use a form like:

$nrconf{override_rc}->{qr(^dbus)} = 1;
$nrconf{override_rc}->{qr(^getty@.+\.servic)} = 1;

For proper behavior, we need to provide a regex that is exactly the same as the one in the default override_rc; needrestart matches against regexes in order and stops on the first match. What if there is a typo, though? Note the "servic" typo in the example above; this is a valid regex, but it's not quite the same as the one in the default override_rc.

Currently, if there are two matching regexes, the one that takes effect is random, with a 50% probability for each. This is due to behavior in relatively modern perl. Perl versions >= 5.18 evaluate hashes in an order that randomly differs from run to run.

https://perldoc.perl.org/perl5180delta

To provide deterministic behavior, sort the keys first. That way, the first matching regex will always win, and the intended override will either always work or never work.

[liske]

Thank you for pointing out this issue! That non-deterministic behavior was not intentional.

(btw: it is possible to remove override_rc entries using delete)

[bugfood]

Thank you for applying this.