Improved production Docker build caching

[9larsons]

Summary

• enables plain BuildKit progress for the production Docker build steps so cache behavior is visible in CI logs
• copies only dependency metadata and component tarballs before pnpm install --prod
• copies the rest of the app after the production dependency install layer
• moves GHOST_BUILD_VERSION until after the expensive install/setup layers so per-commit build versions do not invalidate dependency installation

Expected impact

The current Dockerfile copies the whole packed app and sets GHOST_BUILD_VERSION before running production dependency installation. Because PR builds set GHOST_BUILD_VERSION to the package version plus short SHA, that per-commit value can invalidate the pnpm install --prod layer even when production dependencies are unchanged.

This should make the expensive dependency layer reusable when only app source/admin assets change. The CI logs should also show clearer CACHED/rebuilt layer behavior for the Build & push core image and Build & push full image steps.

Follow-up ideas kept for later

• inspect the first few CI runs after this change and compare Docker layer cache hits/misses with the historic Build & push core image and Build & push full image timings
• consider whether PR E2E needs the exact release-grade image path, or whether main/tags can keep release fidelity while PRs use a faster image path
• consider a docker bake/single multi-target build if the two separate build-push-action calls still duplicate work

Testing

• pnpm --filter ghost archive
• docker buildx build --check --target core -f Dockerfile.production ghost/core/package
• docker buildx build --check --target full -f Dockerfile.production ghost/core/package
• git diff --check

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: 74bca1dd-1228-4c89-833d-18f8ff55774f

📥 Commits

Reviewing files that changed from the base of the PR and between 6f36260 and fb01e7c.

📒 Files selected for processing (2)

• .github/workflows/ci.yml
• Dockerfile.production

✅ Files skipped from review due to trivial changes (1)

• .github/workflows/ci.yml

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Walkthrough

This PR sets BUILDKIT_PROGRESS=plain in step-local env blocks for the CI docker/build-push-action steps that build the core and full images. It also updates Dockerfile.production's core stage: adds ENV NODE_ENV=production near the start, moves corepack enable earlier, narrows initial COPYs to dependency/workspace/registry files plus components, runs pnpm install (and build deps) before copying the rest of the context, separates apt cleanup from subsequent filesystem/setup steps, and relocates ARG/ENV GHOST_BUILD_VERSION to the end of the dependency/setup block.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title 'Improved production Docker build caching' directly matches the main objective of the changeset - optimizing Docker layer caching in production builds.
Description check	✅ Passed	The description is closely related to the changeset, explaining the rationale behind the Docker build and CI workflow changes with clear details about caching improvements.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch codex/improve-production-docker-cache

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 73.81%. Comparing base (88d5d08) to head (6f36260).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #28080   +/-   ##
=======================================
  Coverage   73.80%   73.81%           
=======================================
  Files        1528     1528           
  Lines      129417   129417           
  Branches    15504    15506    +2     
=======================================
+ Hits        95521    95527    +6     
- Misses      32917    32934   +17     
+ Partials      979      956   -23     

Flag	Coverage Δ
admin-tests	54.03% <ø> (ø)
e2e-tests	73.81% <ø> (+<0.01%)	⬆️

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📢 Have feedback on the report? Share it here.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 73.81%. Comparing base (a304042) to head (fb01e7c).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #28080   +/-   ##
=======================================
  Coverage   73.81%   73.81%           
=======================================
  Files        1528     1528           
  Lines      129417   129417           
  Branches    15506    15506           
=======================================
  Hits        95527    95527           
+ Misses      32934    32910   -24     
- Partials      956      980   +24     

Flag	Coverage Δ
admin-tests	54.03% <ø> (ø)
e2e-tests	73.81% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.