ci: add Github Actions workflow to check convergence in a release PR

.github/workflows/dashboard.yaml

@@ -13,4 +13,41 @@ jobs:
       with:
         java-version: 8
     - run: java -version
+    - run: .kokoro/dashboard.sh
+
+  converge:
+    runs-on: ubuntu-latest
+    if: github.repository_owner == 'googleapis' && github.head_ref == 'release-please/branches/master'
+    steps:
+    - uses: actions/checkout@v2
+    - uses: actions/setup-java@v1
+      with:
+        java-version: 8
+      script: |
+        // only approve PRs from release-please
+        if (context.payload.pull_request.user.login !== "release-please") {
+          return;
+        }
+
+        // only approve PRs like "chore: release <release version>"
+        if (!(/^chore: release.*$/.test(context.payload.pull_request.title))) {
+          return;
+        }
+
+        // only approve PRs with README.md, CHANGELOG.md, pom.xml and versions.txt changes
+        const files = new Set(
+          (
+            await github.paginate(
+              github.pulls.listFiles.endpoint({
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                pull_number: context.payload.pull_request.number,
+              })
+            )
+          ).map(file => file.filename)
+        );
+        if (files.size != 4 || !files.has("README.md") || !files.has("CHANGELOG.md") || !files.has("pom.xml") || !files.has("versions.txt")) {
+          return;
+        }
+    - run: java -version
     - run: .kokoro/dashboard.sh

.kokoro/dashboard.sh

@@ -26,3 +26,19 @@ cd dashboard/
 echo -e "\n******************** BUILDING THE DASHBOARD ********************"
 
 mvn --fail-at-end clean install
+INSTALL_RETURN_CODE=$?
+RETURN_CODE=${INSTALL_RETURN_CODE}
+
+case ${JOB_TYPE} in
+converge)
+    mvn exec:java -Dexec.args="-f ../pom.xml --report"
+    CONVERGE_RETURN_CODE=$?
+    if [[ $INSTALL_RETURN_CODE -eq 0 ]]
+    then
+      RETURN_CODE=${CONVERGE_RETURN_CODE}
+    fi
+    ;;
+esac
+
+echo "exiting with ${RETURN_CODE}"
+exit ${RETURN_CODE}