Full cache for offline mode

[samueltaripin]

Merge Checklist

All boxes should be checked before merging the PR

• The changes in the PR have been built and tested
• Documentation has been updated to reflect the changes (or no doc update needed)
• Ready to merge

Description

This PR extends OS package caching to better support “offline” rebuilds by reusing previously downloaded repository metadata, package lists, and cached artifacts across runs.

Changes:

Add persistent caching for RPM metadata (repomd-derived primary location + parsed primary metadata) and DEB parsed package metadata (plus URL existence / package-list URL lookup caches).
Add package-cache “up-to-date” checks to short-circuit downloads when all required DEBs/RPMs are already present locally.
Isolate initrd/chrootenv package download directories and sync initrd packages back into the shared cache; add/adjust tests and release notes.

Any Newly Introduced Dependencies

How Has This Been Tested?

1. run build
2. disconnect from network
3. re-run same build

[Copilot]

Pull request overview

This PR extends OS package caching to better support “offline” rebuilds by reusing previously downloaded repository metadata, package lists, and cached artifacts across runs.

Changes:

• Add persistent caching for RPM metadata (repomd-derived primary location + parsed primary metadata) and DEB parsed package metadata (plus URL existence / package-list URL lookup caches).
• Add package-cache “up-to-date” checks to short-circuit downloads when all required DEBs/RPMs are already present locally.
• Isolate initrd/chrootenv package download directories and sync initrd packages back into the shared cache; add/adjust tests and release notes.

Reviewed changes

Copilot reviewed 22 out of 22 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
internal/ospackage/rpmutils/resolver_test.go	Adds offline-cache tests for RPM metadata parsing and repomd primary location resolution.
internal/ospackage/rpmutils/resolver.go	Implements RPM metadata caching under cache_dir/rpm-metadata with offline-first reads.
internal/ospackage/rpmutils/helper_test.go	Simplifies SPDX filename tests using a regex-based timestamp check.
internal/ospackage/rpmutils/download_cache_test.go	Adds tests for RPM package-cache staleness and cache-clearing behavior.
internal/ospackage/rpmutils/download.go	Adds RPM package-cache staleness detection, cache clearing helpers, and cache short-circuiting.
internal/ospackage/debutils/zip.go	Adds cached package-list URL lookup to avoid repeated probing of Packages.{gz,xz}.
internal/ospackage/debutils/resolver.go	Adds parsed package metadata cache keyed by Release checksum for DEB repos.
internal/ospackage/debutils/helper_test.go	Tightens SPDX filename tests to validate timestamped format via regex.
internal/ospackage/debutils/download_test.go	Adds tests for offline usage of URL/package-list caches and DEB package-cache staleness/clearing.
internal/ospackage/debutils/download.go	Adds persisted URL existence + package-list URL caches, user-repo config init, and DEB cache short-circuiting/clearing.
internal/image/initrdmaker/initrdmaker.go	Downloads initrd packages into an isolated cache dir and syncs them into the shared cache.
internal/image/imageos/imageos_test.go	Updates DEB local repo test harness and mock chroot env to validate metadata refresh call path.
internal/image/imageos/imageos.go	Refreshes local DEB repo metadata as part of DEB local repo initialization.
internal/config/apt_sources_test.go	Adds tests for stable GPG-key cache path and cache-hit behavior.
internal/config/apt_sources_integration_test.go	Minor formatting-only changes.
internal/config/apt_sources.go	Adds persistent caching of downloaded repository GPG keys under cache_dir/gpg-keys.
internal/chroot/chrootbuild/chrootbuild.go	Isolates chrootenv package downloads into a subdir to avoid cache invalidation collisions.
docs/release-notes.md	Documents new GPG key and RPM metadata caching locations/behavior.
cmd/os-image-composer/version_test.go	Fixes ignored errors when closing pipes in tests.
cmd/os-image-composer/completion.go	Handles close/remove errors in dirWritable.
cmd/os-image-composer/cache.go	Handles fmt.Fprintln write errors when printing cache output.
.coverage-threshold	Updates coverage threshold value.