Update GitHub workflows

Author: kddnewton

.github/workflows/auto-merge.yml

@@ -0,0 +1,22 @@
+name: Dependabot auto-merge
+on: pull_request
+
+permissions:
+  contents: write
+  pull-requests: write
+
+jobs:
+  dependabot:
+    runs-on: ubuntu-latest
+    if: ${{ github.actor == 'dependabot[bot]' }}
+    steps:
+      - name: Dependabot metadata
+        id: metadata
+        uses: dependabot/fetch-metadata@v1.3.3
+        with:
+          github-token: "${{ secrets.GITHUB_TOKEN }}"
+      - name: Enable auto-merge for Dependabot PRs
+        run: gh pr merge --auto --merge "$PR_URL"
+        env:
+          PR_URL: ${{github.event.pull_request.html_url}}
+          GITHUB_TOKEN: ${{secrets.GITHUB_TOKEN}}

.github/workflows/main.yml

@@ -18,17 +18,3 @@ jobs:
       run: |
         bundle exec rake test
         bundle exec rake stree:check
-  automerge:
-    name: AutoMerge
-    needs: ci
-    runs-on: ubuntu-latest
-    if: github.event_name == 'pull_request_target' && github.actor == 'dependabot[bot]'
-    steps:
-    - uses: actions/github-script@v3
-      with:
-        script: |
-          github.pulls.merge({
-            owner: context.payload.repository.owner.login,
-            repo: context.payload.repository.name,
-            pull_number: context.payload.pull_request.number
-          })