chore: switch to dependabot builtin from external automerge (#125)

* allow write and use automatic token

* use dependabot metadata to automerge

.github/workflows/auto-merge.yml

@@ -1,16 +1,25 @@
-name: auto-merge
+# https://docs.github.com/en/code-security/dependabot/working-with-dependabot/automating-dependabot-with-github-actions#enable-auto-merge-on-a-pull-request
+name: Dependabot auto-merge
+on: pull_request
 
-on:
-  pull_request_target:
+permissions:
+  contents: write
+  pull-requests: write
 
 jobs:
-  auto-merge:
+  dependabot:
     runs-on: ubuntu-latest
     if: github.actor == 'dependabot[bot]'
     steps:
-    - uses: ahmadnassri/action-dependabot-auto-merge@v2.6
-      with:
-        github-token: '${{ secrets.RHACS_BOT_GITHUB_TOKEN }}'
-        command: "squash and merge"
-        approve: true
-        target: minor
+      - name: Dependabot metadata
+        id: metadata
+        uses: dependabot/fetch-metadata@v2
+        with:
+          github-token: "${{ secrets.GITHUB_TOKEN }}"
+      - name: Enable auto-merge for Dependabot PRs
+        if: steps.metadata.outputs.update-type == 'version-update:semver-minor'
+        run: gh pr merge --auto --squash "$PR_URL"
+        env:
+          PR_URL: ${{github.event.pull_request.html_url}}
+          GH_TOKEN: ${{secrets.GITHUB_TOKEN}}
+