ci: add GitHub Actions workflow for syncing

.github/workflows/sync.yml

@@ -0,0 +1,65 @@
+name: 'Upstream Sync'
+
+permissions:
+  contents: write
+
+on:
+  schedule:
+    - cron: "0 0 * * *" # every day
+
+  workflow_dispatch:  # click the button on Github repo!
+    inputs:
+      sync_test_mode: # Adds a boolean option that appears during manual workflow run for easy test mode config
+        description: 'Fork Sync Test Mode'
+        type: boolean
+        default: false
+
+jobs:
+  sync_latest_from_upstream:
+    runs-on: ubuntu-latest
+    name: Sync latest commits from upstream repo
+    if: ${{ github.event.repository.fork }}
+
+    steps:
+    # Step 1: run a standard checkout action, provided by github
+    - name: Checkout target repo
+      uses: actions/checkout@v3
+      with:
+        # optional: set the branch to checkout,
+        # sync action checks out your 'target_sync_branch' anyway
+        ref:  ${{ secrets.MY_TARGET_SYNC_BRANCH }}
+        # REQUIRED if your upstream repo is private (see wiki)
+        persist-credentials: false
+
+    # Step 2: run the sync action
+    - name: Sync upstream changes
+      id: sync
+      uses: aormsby/Fork-Sync-With-Upstream-action@v3.4.1
+      with:
+        target_sync_branch: ${{ secrets.MY_TARGET_SYNC_BRANCH }}  # need to set
+        # REQUIRED 'target_repo_token' exactly like this!
+        target_repo_token: ${{ secrets.GITHUB_TOKEN }}  # automatically generated, no need to set
+        upstream_sync_branch: main
+        upstream_sync_repo: aormsby/Fork-Sync-With-Upstream-action
+
+        # Set test_mode true during manual dispatch to run tests instead of the true action!!
+        test_mode: ${{ inputs.sync_test_mode }}
+
+    # Step 3: Display a sample message based on the sync output var 'has_new_commits'
+    - name: New commits found
+      if: steps.sync.outputs.has_new_commits == 'true'
+      run: echo "New commits were found to sync."
+
+    - name: No new commits
+      if: steps.sync.outputs.has_new_commits == 'false'
+      run: echo "There were no new commits."
+
+    - name: Show value of 'has_new_commits'
+      run: echo ${{ steps.sync.outputs.has_new_commits }}
+
+    - name: Sync check
+      if: failure()
+      run: |
+        echo "[Error] 由于上游仓库的 workflow 文件变更，导致 GitHub 自动暂停了本次自动更新，你需要手动 Sync Fork 一次"
+        echo "[Error] Due to a change in the workflow file of the upstream repository, GitHub has automatically suspended the scheduled automatic update. You need to manually sync your fork."
+        exit 1