Enable automerge and add Dependabot auto PR merge workflow.

.github/dependabot.yml

@@ -9,4 +9,3 @@ updates:
     directory: "/" # Location of package manifests
     schedule:
       interval: "daily"
-    automerge: true # Enable automerge

.github/workflows/dependabot-auto-pr.yml

@@ -0,0 +1,32 @@
+name: Dependabot auto pr merge
+
+on: pull_request
+
+jobs:
+  dependabot:
+    runs-on: ubuntu-latest
+    # Checking the actor will prevent your Action run failing on non-Dependabot
+    # PRs but also ensures that it only does work for Dependabot PRs.
+    if: ${{ github.actor == 'dependabot[bot]' }}
+    steps:
+      # This first step will fail if there's no metadata and so the approval
+      # will not occur.
+      - name: Dependabot metadata
+        id: dependabot-metadata
+        uses: dependabot/[email protected]
+        with:
+          github-token: "${{ secrets.GITHUB_TOKEN }}"
+      # Here the PR gets approved.
+      - name: Approve a PR
+        run: gh pr review --approve "$PR_URL"
+        env:
+          PR_URL: ${{ github.event.pull_request.html_url }}
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+      # Finally, this sets the PR to allow auto-merging for patch and minor
+      # updates if all checks pass
+      - name: Enable auto-merge for Dependabot PRs
+        if: ${{ steps.dependabot-metadata.outputs.update-type != 'version-update:semver-major' }}
+        run: gh pr merge --auto --squash "$PR_URL"
+        env:
+          PR_URL: ${{ github.event.pull_request.html_url }}
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}