Add bootc imagectl: Rust reimplementation of bootc-base-imagectl

[jeckersb]

Implements a new bootc imagectl command that provides container image
build tooling, reimplementing the Python bootc-base-imagectl script in Rust.

This adds a new bootc-imagectl crate with three main subcommands:

• list: List available rpm-ostree manifests with descriptions
• rechunk: Generate chunked OCI images using rpm-ostree
• build-rootfs: Build container root filesystems from manifests

The build-rootfs command supports:

• Custom manifests with JSON overrides
• Additional package installation (--install)
• OSTree directory overlays (--add-dir)
• Package version locking via NEVRA/NEVR (--lock)
• Repository selection (--repo)
• Documentation control (--no-docs)
• Sysusers configuration (--sysusers)
• Build configuration reinjection (--reinject)

Key features:

• Full feature parity with Python implementation
• Comprehensive input validation and error handling
• Modular design with separate manifest, lockfile, and build modules
• Automatic cleanup of temporary files via RAII
• 7 unit tests covering validation and NEVRA parsing
• Accessible via both bootc imagectl and bootc image-build alias

Container testing shows identical output to the Python version for the
list command and proper error handling for build operations.

🤖 Generated with Claude Code

Co-Authored-By: Claude noreply@anthropic.com

[jeckersb]

100% just turning claude loose on "rewrite bootc-base-imagectl in rust" with some very minor nudges along the way. It did at least superficially sanity check this in a container against the python implementation, but I haven't tested anything. Just wanted to post it before disappearing for the holiday 👋

[cgwalters]

I definitely think the tool needs a rewrite and more productization, but in the current vision of this project bootc is not itself a buildsystem or tied to any specific OS or distro. Calling out to apt/dnf/rpm-ostree and such should be done in general via "plugins" if we need it - that's what we do with system-reinstall-bootc.

Options:

• Move into Fedora namespace
• Create bootc-dev/fedora-base-imagectl

Of course it might not be too hard for this tool to grow package abstractions, and it could become bootc-dev/<bikeshed>-imagectl here. But still though I think a core principle of this project is that we boot OCI images and should support multiple build systems.

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That said I think it does make sense to chip away at things from the "bottom"; a wrapper for ukify seems reasonably self contained for example.

[cgwalters]

Per discussion above, closing this, let's instead keep up momentum on the work items in #1498 as well as https://gitlab.com/fedora/bootc/docs/-/merge_requests/143 !