ostree-ext: reuse prior packing with exclusive components

[officialasishkumar]

Summary

Reuse the prior-build packing layout when exclusive components have already been split into dedicated layers.

Changes

• drop prior-build bins that become empty after exclusive components are filtered out
• keep the trailing reserved "new packages" bin so added regular components still have a stable destination
• add a regression test covering prior-build reuse with exclusive components

Testing

• cargo fmt --check --all
• docker run --rm -v /home/ashish/asish_workspace/personal/bootc:/src -w /src fedora:42 bash -lc 'set -euo pipefail && dnf -y install rust cargo pkgconf-pkg-config glib2-devel ostree-devel openssl-devel systemd-devel libzstd-devel git gcc make && cargo test -p ostree-ext test_advanced_packing -- --nocapture && cargo test -p ostree-ext test_exclusive_chunks -- --nocapture'

Fixes #2057

[gemini-code-assist]

Code Review

The pull request modifies the basic_packing_with_prior_build function in crates/ostree-ext/src/chunking.rs to correctly handle exclusive-component bins. It introduces logic to filter out empty bins from the prior build while ensuring the final reserved bin for new packages is preserved. Additionally, the bin size validation check has been moved to execute after this filtering process. A new test case, test_advanced_packing_with_prior_exclusive_components, was added to verify that the prior layout remains reusable after exclusive bins are removed. I have no feedback to provide.

[jmarrero]

This seems pretty good, the failures seem like flakes. Thanks @officialasishkumar you had something else you wanted to add?

[officialasishkumar]

@jmarrero Nothing else to add from my side right now. I refreshed the branch onto current main, and I will keep an eye on the flakes and the updated checks.