ci: add merge_group trigger to enable GitHub merge queue

[Marzooqa]

Summary

Wires up the merge_group event in ci.yml so GitHub's merge queue has CI checks to gate on before landing PRs on master.

• Add merge_group: types: [checks_requested] trigger
• Fall back to github.sha for checkout ref (PR sha is null in queue context)
• Fall back to master for GITHUB_BASE_REF when unset (merge_group context)
• Skip commit-lint in merge_group — commits already vetted when the PR's own CI ran

The existing all-checks umbrella job serves as the required status check — no new jobs needed.

Remaining step (requires repo admin)

In Settings → Branches → Edit rule for master:

• Enable Require merge queue
• Strategy: ALLGREEN
• Required status check: all-checks
• Max entries to build: 2
• Timeout: 60–120 min

Linear

WCI-1097

[linear-code]

WCI-1097

[Marzooqa]

@claude

[github-actions]

Claude finished @Marzooqa's task —— View job

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Code Review Progress

• Read and analyze CI workflow changes
• Review merge_group implementation approach
• Check for potential issues and improvements
• Provide comprehensive review feedback

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Code Review: GitHub Merge Queue Implementation

This PR correctly implements GitHub merge queue support in the CI workflow. The changes are well-thought-out and address the key requirements for merge queue functionality.

✅ Strengths

1. Proper Event Trigger Configuration

merge_group:
  types: [checks_requested]

• Correctly uses checks_requested trigger type for merge queue events
• Follows GitHub's recommended pattern for merge queue integration

2. Robust Checkout Reference Handling

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

• Smart fallback from PR head sha to github.sha for merge_group context (lines 71, 141, 198, 292, 366, 377, 394)
• Prevents checkout failures when github.event.pull_request.head.sha is null in merge queue context

3. Base Reference Fallback Logic

git fetch origin ${GITHUB_BASE_REF:-master}
GITHUB_REPO_BRANCH=${GITHUB_BASE_REF:-master} yarn run check-commits

• Properly handles missing GITHUB_BASE_REF environment variable in merge_group context (lines 90, 172-173)
• Falls back to master branch when base ref is unset

4. Selective Commit Linting

if: matrix.check == 'commit-lint' && github.event_name != 'merge_group'

• Intelligently skips commit linting for merge_group events (line 170)
• Avoids redundant checks since commits were already validated during PR CI

5. Path Filter Updates

• Updated comment on line 24 correctly describes new behavior including merge_group
• changes job properly skips for merge_group, allowing dependent jobs to run unconditionally

🔍 Technical Analysis

Changes Job Behavior: The changes job only runs on pull_request events, which means for merge_group events it will be skipped. This causes downstream jobs that depend on it to run unconditionally (due to needs.changes.result == 'skipped' condition), which is the correct behavior for merge queue validation.

All-Checks Job: The existing all-checks umbrella job will serve as the required status check for merge queue, requiring no changes. This is a good architectural decision.

⚠️ Minor Observations

1. Consistency Check: All checkout actions consistently use the same fallback pattern - good job maintaining consistency across 7 different checkout steps.

2. Environment Variable Handling: The bash parameter expansion ${GITHUB_BASE_REF:-master} is used consistently in both git fetch and environment variable contexts.

📋 Verification Checklist

• merge_group trigger properly configured
• Checkout references handle null PR sha in merge context
• Base reference fallbacks prevent fetch failures
• Commit linting appropriately skipped for merge_group
• Path filtering logic updated for new event type
• No breaking changes to existing PR/push workflows

🎯 Recommendation

APPROVE - This is a solid implementation that follows GitHub merge queue best practices. The changes are minimal, focused, and address all the key requirements:

1. ✅ Enables CI to run on merge queue events
2. ✅ Handles context differences between PR and merge_group events
3. ✅ Avoids redundant validation steps
4. ✅ Maintains backward compatibility with existing workflows

The implementation is ready for the next step: enabling merge queue in branch protection settings with all-checks as the required status check.

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Job Run | Branch: WCI-1097-enable-merge-queue-on-bitgojs