Add auto-merge workflow for dependabot

.github/workflows/auto-merge.yml

@@ -0,0 +1,29 @@
+name: Dependabot and Pre-commit auto-merge
+
+# This workflow is triggered when a PR is opened or synchronized
+# by dependabot or pre-commit-ci. It will approve and merge the PR
+# automatically.
+
+# Source: auto-merge.yml from dalonsoa and alexdewar
+
+on:
+  pull_request:
+
+permissions:
+  contents: write
+  pull-requests: write # Needed if in a private repository
+
+jobs:
+  auto-merge:
+    runs-on: ubuntu-latest
+    if: ${{ github.event.pull_request.user.login == 'dependabot[bot]' || github.event.pull_request.user.login == 'pre-commit-ci[bot]' }}
+    steps:
+      - name: Enable auto-merge for dependabot and pre-commit-ci PRs
+        run: |
+          gh pr review --approve "$PR_URL"
+          gh pr merge --auto --merge "$PR_URL"
+        env:
+          PR_URL: ${{ github.event.pull_request.html_url }}
+          # GitHub provides this variable in the CI env. You don't
+          # need to add anything to the secrets vault.
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}