to-disk: Add support for --karg

[cgwalters]

For the same reason we propagate other options.

[gemini-code-assist]

Summary of Changes

Hello @cgwalters, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a significant enhancement by adding support for the --karg command-line option, which enables the specification of custom kernel arguments. This allows for more granular control over kernel behavior during the installation of disk images and the execution of virtual machines. The change includes updates to the core argument parsing logic, comprehensive integration tests to validate the functionality, and thorough documentation across relevant man pages to ensure users can effectively leverage this new capability.

Highlights

• New Feature: Kernel Argument Support: Introduced the --karg option to allow users to pass custom kernel arguments during disk image installation and virtual machine execution, enhancing system configuration flexibility.
• Core Logic Implementation: The InstallOptions struct in crates/kit/src/install_options.rs now includes a karg field, and its to_args method correctly serializes these arguments for command-line usage.
• Integration Test Verification: Updated integration tests in crates/integration-tests/src/tests/libvirt_verb.rs to include and verify the successful propagation of a test kernel argument via SSH into the VM's /proc/cmdline.
• Documentation Updates: Man pages for bcvk-libvirt-run, bcvk-libvirt-upload, and bcvk-to-disk have been updated to clearly document the new --karg option and its usage.
• Code Refactoring: Minor cleanup in crates/kit/src/cache_metadata.rs test cases, refactoring InstallOptions initialization to use ..Default::default() for improved readability and conciseness.

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[gemini-code-assist]

Code Review

This pull request adds support for a --karg option to propagate kernel arguments to bootc install for to-disk, libvirt-run, and libvirt-upload commands. The implementation adds the karg field to InstallOptions and updates the argument construction and documentation.

The changes look good overall, but I've found a few issues. Most importantly, there appears to be a critical issue in an unmodified file, crates/kit/src/libvirt/run.rs, which prevents the new --karg option from working with the libvirt run command. The kernel arguments are not passed to the disk creation logic because at line 164, &[] is passed for kernel_args instead of &opts.install.karg. Since I cannot comment on unmodified files, I'm highlighting this here.

Additionally, I've left a few comments regarding:

• Inconsistent argument formatting for the bootc command.
• Duplicated options in some of the updated man pages.
• An outdated assertion message in an integration test.

Please see my detailed comments for suggestions on how to fix these.