RFE: Add a hidden option to `rpm-ostree kargs` to update all existing deployments in place

[travier]

Describe the enhancement

Add a hidden option to rpm-ostree kargs to update all existing deployments in place.

Example:

$ sudo rpm-ostree kargs --append-if-missings=rw --all-deployments

This would be useful for: https://fedoraproject.org/wiki/Changes/Silverblue_Kinoite_readonly_sysroot

I will work on this one if there is agreement that this is something we are OK with.

This is also a potential 'good first issue' if someone is interested.

[cgwalters]

Seems sane to me, although perhaps the CLI flag should only affect deployments with a matching stateroot? Dunno. Probably obscure enough to not matter.

[jlebon]

This is what rdcore kargs does, which it makes sense to have native support for in the rpm-ostree stack. Hmm, though I wonder if it should be in ostree instead since it's really common to all ostree consumers. Possibly extending the existing hidden ostree admin instutil set-kargs command.

[dustymabe]

Any need to bring this up in the meeting this week?

[travier]

I mistakenly filed this in the FCOS tracker as I originally wanted to file it in the rpm-ostree tracker. Not sure this is meeting worthy.

[travier]

This has been implemented in ostree: https://github.com/ostreedev/ostree/issues/2590.