fix(supply-chain): pass --source-digest from promote-core to the lock updater

[williaby]

Summary

While validating the supply-chain reusable workflows (#234) ahead of wiring the first caller, I found a deterministic contract bug between promote-core and the per-repo lock updater it invokes.

supply-chain-promote-core.yml's update-lock job shells out to the caller repo's scripts/update_approved_lock.py, but never passes --source-digest, which that script marks required=True. Every write_lock: true run would die at the lock step with:

update_approved_lock.py: error: the following arguments are required: --source-digest

CI never caught it because no caller exists yet, so the update-lock job has never executed.

Fix

Derive the source digest in the job and pass it:

• Mirror path (source_kind=registry): the upstream digest embedded in source_ref (registry/name@sha256:...). crane copy-by-digest preserves it, so source_digest == target_digest and the lock records the equality the schema intends.
• Build path (source_kind=oci-tar): no separate upstream, so it collapses to the target digest.

The derived value is shape-guarded (^sha256:[0-9a-f]{64}$) before it reaches the updater.

Validation

• python3 -c yaml.safe_load parses clean; actionlint clean; all pre-commit hooks pass.
• This is a prerequisite for the first P3 caller (container-images public mirror) to write the approved-lock without failing.

Context

Found during Task P3 (route both repos through the shared trust core). Two further P3 gates surfaced in the same validation pass and are tracked separately: the homelab-infra private-overlay updater/schema (P2 deliverable, not yet present) and the Trivy re-vetting #VERIFY baked into promote-core (PR #229 removed Trivy after its March 2026 release-infra compromise).

Generated with Claude Code

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[coderabbitai]

Warning

Review limit reached

@williaby, you've reached your PR review limit, so we couldn't start this review.

Next review available in: 44 minutes

Enable usage-based reviews in Billing to review now. Otherwise, wait until the next included review is available.
You're only billed for reviews past your plan's rate limits ($0.25/file).

How can I continue?

After more reviews become available, a review can be triggered using the @coderabbitai review command as a PR comment. Alternatively, push new commits to this PR.

To avoid repeated limits, reduce automatic review volume by pausing incremental auto-reviews earlier, using label-based review opt-in, excluding WIP or generated PR titles, or requesting reviews manually when the PR is ready. If your team needs uninterrupted high-volume reviews, an organization admin can enable usage-based reviews.

How do review limits work?

CodeRabbit enforces per-developer PR review limits for each organization. Most developers receive the normal plan review availability.

For paid Pro and Pro+ PR reviews, CodeRabbit uses adaptive limits for sustained high-volume activity. When a developer's recent PR review activity reaches the 95th percentile or higher among CodeRabbit users, additional reviews become available more gradually as earlier reviews age out of the rolling window.

Please refer docs for additional details.

Review details

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: d60f070a-ef42-4908-bdbc-2d84f84c5ee1

📥 Commits

Reviewing files that changed from the base of the PR and between c7fb2b4 and 58e1220.

📒 Files selected for processing (1)

• .github/workflows/supply-chain-promote-core.yml

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/promote-core-source-digest

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}