Add workflow for auto-merging Dependabot updates

Author: firefart

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

@@ -0,0 +1,28 @@
+name: Auto-merge dependabot updates
+
+on:
+  pull_request:
+    branches: [main]
+
+permissions:
+  pull-requests: write
+  contents: write
+
+jobs:
+  dependabot-merge:
+    runs-on: ubuntu-latest
+    if: ${{ github.actor == 'dependabot[bot]' }}
+    steps:
+      - name: Dependabot metadata
+        id: metadata
+        uses: dependabot/fetch-metadata@v2.4.0
+        with:
+          github-token: "${{ secrets.GITHUB_TOKEN }}"
+
+      - name: Enable auto-merge for Dependabot PRs
+        # Only if version bump is not a major version change
+        if: ${{steps.metadata.outputs.update-type != 'version-update:semver-major'}}
+        run: gh pr merge --auto --merge "$PR_URL"
+        env:
+          PR_URL: ${{github.event.pull_request.html_url}}
+          GITHUB_TOKEN: ${{secrets.GITHUB_TOKEN}}