Add hooks for deployment steps to allow bootloader swapping

[Mstrodl]

Can be used to provide hooks into a sysroot deploy for tools like bootupd to perform bootloader swaps.

Happy to do this a different way, but this is how we've been doing it on our debian-based system. I understand bootupd is supposed to work a different way. We do it this way because grub-mkconfig will generate a broken config for the older version of grub.

See #3496 for motivation

[openshift-ci]

Hi @Mstrodl. Thanks for your PR.

I'm waiting for a github.com member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

I understand the commands that are listed here.

Details

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[gemini-code-assist]

Code Review

This pull request adds support for a bootloader-plugin by introducing hooks into the deployment process. The overall logic is sound, with hooks for deploy and swap actions placed at appropriate stages. My main feedback concerns code duplication in the plugin invocation logic, which could be refactored into a helper function for better maintainability. Additionally, the path to the plugin executable is hardcoded, and making it configurable would enhance flexibility for different system layouts.

[Mstrodl]

By the way if this is not something you guys want to take, that's fine too. I just figured other people might find it useful too :)

[champtar]

One important info from #3496 that you forgot to repeat here is that Debian version of grub doesn't support BLS (yet), so you can't use bootupd static config :(

[Mstrodl]

Hmm
Tests keep failing in different spots, but they look pretty unrelated. Is there some way to retry the jenkins one @cgwalters?

Also if it would be helpful I could share the source for our grub plugin. It's not perfectly atomic, but it's better than nothing :)