Use merge queue

.github/workflows/ci.yml

@@ -1,11 +1,9 @@
 name: CI
 
 on:
-  pull_request:
+  merge_group:
 
-  push:
-    branches:
-      - master
+  pull_request:
 
   # smoelius: Every Thursday at 3:00 UTC (Wednesday at 22:00 EST), run `cargo test -- --ignored`.
   schedule:
@@ -21,7 +19,41 @@ env:
   CARGO_TERM_COLOR: always
 
 jobs:
+  maybe-expedite:
+    outputs:
+      value: ${{ steps.expedite.outputs.value }}
+
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Log github refs
+        run: |
+          echo '```' >> "$GITHUB_STEP_SUMMARY"
+          echo 'github.ref: ${{ github.ref }}' >> "$GITHUB_STEP_SUMMARY"
+          echo 'github.sha: ${{ github.sha }}' >> "$GITHUB_STEP_SUMMARY"
+          echo '```' >> "$GITHUB_STEP_SUMMARY"
+
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Check if merging an up-to-date branch
+        if: ${{ github.event_name == 'merge_group' }}
+        id: expedite
+        run: |
+          N="$(expr "${{ github.ref }}" : '.*-\([0-9]\+\)-[^-]*$')"
+          BASE_SHA="$(gh api /repos/${{ github.repository }}/pulls/"$N" | jq -r '.base.sha')"
+          if git diff --quiet ${{ github.event.merge_group.base_sha }} "$BASE_SHA"; then
+            echo "value=1" >> "$GITHUB_OUTPUT"
+          fi
+        env:
+          GH_TOKEN: ${{ github.token }}
+
   lint:
+    needs: [maybe-expedite]
+
+    if: ${{ ! needs.maybe-expedite.outputs.value }}
+
     runs-on: ubuntu-latest
 
     steps:
@@ -99,6 +131,10 @@ jobs:
           cargo clean && cargo +nightly udeps --all-targets
 
   test:
+    needs: [maybe-expedite]
+
+    if: ${{ ! needs.maybe-expedite.outputs.value }}
+
     runs-on: ubuntu-latest
 
     strategy: