add auto-merge-check-pr workflow

Author: leona-ya

.github/workflows/auto-merge-check-pr.yaml

@@ -0,0 +1,31 @@
+name: "Check auto-mergeability of PR"
+on:
+  # use pull_request_target to also run on PRs with merge conflict
+  pull_request_target:
+    types: [labeled, unlabeled, ready_for_review]
+  pull_request_review:
+    types: [submitted, dismissed]
+
+permissions:
+  contents: read
+  statuses: write
+  pull-requests: write
+  issues: write
+
+jobs:
+  action:
+    name: check-auto-mergeability-of-pr
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          repository: flyingcircusio/fc-nixos-release-tools
+          ref: 'PL-133248-auto-merge'
+      - uses: cachix/install-nix-action@v30
+      - name: build release tooling
+        run: |
+          nix build .#
+      - run: |
+          ./result/bin/auto-merge check-pr ${{ github.event.number }}
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}