fix: refactor cache-checkout to use actions/cache@v4 with fallback

[keithwillcode]

What does this PR do?

Fixes cache propagation delay issues with Blacksmith's distributed cache that were causing CI failures.

Root cause: The Prepare job saves the cache, but subsequent jobs starting ~14 seconds later couldn't find it because the cache hadn't propagated yet in Blacksmith's distributed system. The previous implementation used separate actions/cache/save@v4 and actions/cache/restore@v4 with fail-on-cache-miss: true, which caused immediate failures.

Solution: Refactored cache-checkout to use actions/cache@v4 (combined save/restore) with a fallback to do the checkout if cache miss occurs. This matches the pattern used by cache-build and cache-db which don't have this issue.

Changes:

• Refactored cache-checkout action to use actions/cache@v4 instead of separate save/restore
• Added fallback checkout step when cache miss occurs (using same sparse-checkout config as dangerous-git-checkout)
• Removed mode input (no longer needed)
• Updated all 19 workflow files to use the simplified cache-checkout action
• Removed separate dangerous-git-checkout step from pr.yml Prepare job (now handled by cache-checkout)

Mandatory Tasks (DO NOT REMOVE)

• I have self-reviewed the code (A decent size PR without self-review might be rejected).
• I have updated the developer docs in /docs if this PR makes changes that would require a documentation change. N/A - CI workflow changes only.
• I confirm automated tests are in place that prove my fix is effective or that my feature works. N/A - CI workflow changes can only be tested by running the actual CI pipeline.

How should this be tested?

1. Create/update a PR to trigger the CI workflow
2. Observe the Prepare job - it should save the cache on first run (cache miss triggers checkout)
3. Observe subsequent jobs (type-check, lint, etc.) - they should either:
   • Hit the cache and skip checkout, OR
   • Miss the cache and perform checkout via the fallback step (instead of failing)
4. Verify all CI jobs complete successfully

Checklist

• My code follows the style guidelines of this project
• I have checked if my changes generate no new warnings

Human Review Checklist

• Verify the fallback checkout uses correct ref (github.event.pull_request.head.sha) in all workflow contexts
• Confirm cache key format is unchanged for backward compatibility
• Run CI on this PR to validate the fix works

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[keithwillcode]

Testing here https://github.com/calcom/cal.com/actions/runs/20883169550/job/60002519992

[keithwillcode]

And here https://github.com/calcom/cal.com/actions/runs/20883198261

[cubic-dev-ai]

1 issue found across 20 files

Prompt for AI agents (all issues)

Check if these issues are valid — if so, understand the root cause of each and fix them.


<file name=".github/actions/cache-checkout/action.yml">

<violation number="1" location=".github/actions/cache-checkout/action.yml:20">
P1: Missing fallback for `ref` parameter will break this action in non-PR contexts (e.g., `workflow_dispatch`). The cache key correctly uses `${{ github.event.pull_request.head.sha || github.sha }}` but the checkout `ref` lacks the same fallback.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.}

[cubic-dev-ai]

P1: Missing fallback for ref parameter will break this action in non-PR contexts (e.g., workflow_dispatch). The cache key correctly uses ${{ github.event.pull_request.head.sha || github.sha }} but the checkout ref lacks the same fallback.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At .github/actions/cache-checkout/action.yml, line 20:

<comment>Missing fallback for `ref` parameter will break this action in non-PR contexts (e.g., `workflow_dispatch`). The cache key correctly uses `${{ github.event.pull_request.head.sha || github.sha }}` but the checkout `ref` lacks the same fallback.</comment>

<file context>
@@ -1,33 +1,26 @@
-          !node_modules
-          !**/node_modules
-        key: git-checkout-${{ github.head_ref || github.ref_name }}-${{ github.event.pull_request.head.sha || github.sha }}
+        ref: ${{ github.event.pull_request.head.sha }}
+        fetch-depth: 2
+        sparse-checkout-cone-mode: false
</file context>

_{Fix confidence (alpha): 10/10}

Suggested change

	ref: ${{ github.event.pull_request.head.sha }}
	ref: ${{ github.event.pull_request.head.sha || github.sha }}

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