Proposal: Configure merge_queue on the repository (to replace tide)

.github/workflows/ci.yaml

@@ -1,6 +1,8 @@
 name: ci
 
-on: [pull_request]
+on:
+  pull_request: {}
+  merge_group: {}
 
 concurrency:
   group: ${{ github.workflow }}-${{ github.event.pull-request.number || github.ref }}
@@ -174,3 +176,5 @@ jobs:
   e2e-tests:
     needs: [build]
     uses: ./.github/workflows/e2e-matrix.yml
+    with:
+      minimal: ${{ github.event_name == 'merge_group' }}

.github/workflows/dependency-review.yml

@@ -7,7 +7,9 @@
 #
 # Source repository: https://github.com/actions/dependency-review-action
 name: 'Dependency Review'
-on: [pull_request]
+on:
+  pull_request:
+  merge_group:
 
 permissions:
   contents: read

.github/workflows/e2e-matrix.yml

@@ -1,51 +1,59 @@
 name: Tekton Integration
 # Adapted from https://github.com/mattmoor/mink/blob/master/.github/workflows/minkind.yaml
 
-on: [workflow_call]
+on:
+  workflow_call:
+    inputs:
+      minimal:
+        description: 'Run minimal matrix (aka only one job)'
+        required: false
+        type: boolean
+        default: false
 
 defaults:
   run:
     shell: bash
 
 jobs:
+  generate-matrix:
+    runs-on: ubuntu-latest
+    outputs:
+      matrix: ${{ steps.set-matrix.outputs.matrix }}
+    steps:
+    - id: set-matrix
+      run: |
+        if [[ "${{ inputs.minimal }}" == "true" ]]; then
+          # Minimal set: only one job
+          matrix='{"include":[{"os":"ubuntu-latest","k8s-name":"k8s-latest","k8s-version":"v1.34.x","feature-flags":"stable"}]}'
+        else
+          # Full matrix:
+          # - amd64: all combinations (2 k8s versions x 3 feature flags = 6 jobs)
+          # - arm64: only k8s-latest with stable (1 job)
+          # Total: 7 jobs
+          matrix='{
+            "include": [
+              {"os": "ubuntu-latest", "k8s-name": "k8s-oldest", "k8s-version": "v1.28.x", "feature-flags": "stable"},
+              {"os": "ubuntu-latest", "k8s-name": "k8s-oldest", "k8s-version": "v1.28.x", "feature-flags": "beta"},
+              {"os": "ubuntu-latest", "k8s-name": "k8s-oldest", "k8s-version": "v1.28.x", "feature-flags": "alpha"},
+              {"os": "ubuntu-latest", "k8s-name": "k8s-latest", "k8s-version": "v1.34.x", "feature-flags": "stable"},
+              {"os": "ubuntu-latest", "k8s-name": "k8s-latest", "k8s-version": "v1.34.x", "feature-flags": "beta"},
+              {"os": "ubuntu-latest", "k8s-name": "k8s-latest", "k8s-version": "v1.34.x", "feature-flags": "alpha"},
+              {"os": "ubuntu-24.04-arm", "k8s-name": "k8s-latest", "k8s-version": "v1.34.x", "feature-flags": "stable"}
+            ]
+          }'
+        fi
+        echo "matrix=$(echo $matrix | jq -c .)" >> $GITHUB_OUTPUT
+
   e2e-tests:
+    needs: generate-matrix
     concurrency:
       group: ${{ github.workflow }}-${{ matrix.os }}-${{ matrix.k8s-name }}-${{ matrix.feature-flags }}-${{ github.event.pull_request.number || github.ref }}
       cancel-in-progress: true
     name: e2e tests
     runs-on: ${{ matrix.os }}
     strategy:
       fail-fast: false # Keep running if one leg fails.
-      matrix:
-        os:
-        - ubuntu-latest     # amd64
-        - ubuntu-24.04-arm  # arm64
-
-        k8s-name:
-        - k8s-oldest             # 1.28
-        - k8s-latest             # 1.34
-
-        feature-flags:
-        - stable
-        - beta
-        - alpha
-
-        include:
-        - k8s-name: k8s-oldest
-          k8s-version: v1.28.x
-        - k8s-name: k8s-latest
-          k8s-version: v1.34.x
-
-        # Limit arm64: only run k8s-latest on arm64 (alpha and beta), skip oldest on arm64
-        exclude:
-        - k8s-name: k8s-oldest
-          os: ubuntu-24.04-arm
-        - k8s-name: k8s-latest
-          os: ubuntu-24.04-arm
-          feature-flags: beta
-        - k8s-name: k8s-latest
-          os: ubuntu-24.04-arm
-          feature-flags: alpha
+      matrix: ${{ fromJSON(needs.generate-matrix.outputs.matrix) }}
     env:
       KO_DOCKER_REPO: registry.local:5000/tekton
       CLUSTER_DOMAIN: c${{ github.run_id }}.local
@@ -54,7 +62,7 @@ jobs:
 
     steps:
     - name: Free disk space
-      if: ${{ matrix.os != 'ubuntu-24.04-arm' }}
+      if: matrix.os != 'ubuntu-24.04-arm'
       run: |
         echo "--- Disk space before cleanup ---"
         df -h

.github/workflows/go-coverage.yml

@@ -6,6 +6,7 @@ permissions:
 on:
   pull_request:
     branches: ["main"]
+  merge_group:
   push:
     branches: ["main"]
   # run at least once every 2 months to prevent the coverage artifact from expiring

DEVELOPMENT.md

@@ -292,6 +292,60 @@ as follows.
 
 ---
 
+## Pull Request Merge Queue
+
+This repository uses GitHub's merge queue to ensure the `main` branch remains stable and free from integration conflicts. The merge queue automatically validates that approved pull requests can be merged cleanly with the latest version of `main` before allowing them to land.
+
+### How It Works
+
+When your pull request is approved and all required checks pass:
+
+1. **Add to Queue**: An approver adds your PR to the merge queue (either manually or automatically based on labels/approvals)
+2. **Temporary Merge**: GitHub creates a temporary branch (`gh-readonly-queue/main/pr-{number}-{sha}`) that merges your PR with the latest `main`
+3. **Validation**: Required CI checks run on this merged state to verify compatibility
+4. **Automatic Merge**: If all checks pass, your PR is automatically merged to `main`
+5. **Failure Handling**: If checks fail on the merged state, your PR is removed from the queue and you'll need to rebase/fix conflicts
+
+### CI Behavior in Merge Queue
+
+To keep the merge queue fast and efficient, the CI matrix is optimized differently for merge queue builds versus regular PR builds:
+
+**Regular Pull Request Builds:**
+- Full e2e test matrix: 18 configurations
+  - 2 architectures (amd64, arm64)
+  - 2 Kubernetes versions (1.28, 1.34)
+  - 3 feature flag sets (stable, beta, alpha)
+- Comprehensive validation before approval
+
+**Merge Queue Builds:**
+- Minimal e2e test matrix: 1 configuration
+  - Single architecture: ubuntu-latest (amd64)
+  - Latest Kubernetes: 1.34
+  - Stable feature flags only
+- Faster validation focused on integration conflicts
+- Full matrix already validated during PR review
+
+This optimization significantly reduces merge queue time while maintaining safety, since your PR has already passed the full 18-configuration test matrix during review.
+
+### What You Need to Know
+
+- **PR reviews unchanged**: Continue developing and testing PRs as usual - all checks must pass before your PR can enter the queue
+- **Automatic process**: Once approved, the merge queue handles merging automatically
+- **Stay up-to-date**: Keep your PR rebased on `main` to minimize queue failures
+- **Queue failures**: If your PR fails in the queue, check for:
+  - Merge conflicts with recent changes to `main`
+  - Integration issues with other recently merged PRs
+  - Flaky tests (less common with minimal matrix)
+
+### Benefits
+
+- **Never break main**: Changes are only merged if they work with the latest code
+- **No merge conflicts**: Incompatible changes are detected before landing
+- **Reduced CI load**: Optimized test matrix for queue builds saves resources
+- **Higher velocity**: Automated merging eliminates manual merge bottlenecks
+
+---
+
 ## Building and deploying
 
 ### Setup a Kubernetes cluster