Auto-label PRs by outside collaborators (#648)

b/261052420

.github/workflows/auto_assign.yaml

@@ -0,0 +1,35 @@
+name: PR Reviewer Auto Assignment
+
+on:
+  pull_request_target:
+    types:
+      - opened
+      - reopened
+
+concurrency:
+  group: '${{ github.workflow }}-${{ github.event_name }} @ ${{ github.event.pull_request.number || github.sha }}'
+  cancel-in-progress: true
+
+jobs:
+  assign-reviewer:
+    runs-on: ubuntu-latest
+    permissions:
+      pull-requests: write
+    steps:
+    - name: Check if PR author is outside collaborator and assign reviewer
+      env:
+        PR_AUTHOR_LOGIN: ${{ github.event.pull_request.user.login }}
+        REPO_NAME: ${{ github.event.repository.full_name }}
+        PR_NUMBER: ${{ github.event.number }}
+      run: |
+        PERMISSION_LEVEL=$(curl -s -H "Authorization: token ${{ secrets.GITHUB_TOKEN }}" \
+          "https://api.github.com/repos/$REPO_NAME/collaborators/$PR_AUTHOR_LOGIN/permission" | jq -r .role_name)
+
+        if [ "$PERMISSION_LEVEL" == "none" ] || [ "$PERMISSION_LEVEL" == "read" ]; then
+          echo "PR author is an outside collaborator. Adding label..."
+
+          curl -s -X POST -H "Authorization: token ${{ secrets.GITHUB_TOKEN }}" \
+            -H "Accept: application/vnd.github.v3+json" \
+            -d '["outside collaborator"]' \
+            "https://api.github.com/repos/$REPO_NAME/issues/$PR_NUMBER/labels"
+        fi