ci: automate rebasing fork onto upstream

Author: pexcn

.github/workflows/rebase-upstream.yml

@@ -0,0 +1,34 @@
+name: Rebase upstream
+
+on:
+  workflow_dispatch:
+  schedule:
+    - cron: "30 3 * * *"
+      timezone: "Asia/Taipei"
+
+permissions:
+  contents: write
+
+concurrency:
+  group: rebase-upstream
+  cancel-in-progress: false
+
+jobs:
+  sync:
+    runs-on: ubuntu-24.04
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v7
+        with:
+          ref: main
+          fetch-depth: 0
+          ssh-key: ${{ secrets.SSH_KEY }}
+      - name: Rebase upstream
+        run: |
+          set -e
+          git config user.name "github-actions[bot]"
+          git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
+          git remote add upstream https://github.com/docker/github-builder.git
+          git fetch upstream main
+          git rebase upstream/main
+          git push origin HEAD:main --force-with-lease