fix: sync 内容一致时改为对齐上游，避免历史分叉越积越多

Author: chengww

.github/workflows/sync.yml

@@ -15,26 +15,28 @@ jobs:
     if: ${{ github.event.repository.fork }}
 
     steps:
-      # Step 1: run a standard checkout action
       - name: Checkout target repo
         uses: actions/checkout@v6
+        with:
+          fetch-depth: 0
 
-      # Step 2: run the sync action
       - name: Sync upstream changes
-        id: sync
-        uses: aormsby/fork-sync-with-upstream-action@v3.4.3
-        with:
-          upstream_sync_repo: cmliu/edgetunnel
-          upstream_sync_branch: main
-          target_sync_branch: main
-          target_repo_token: ${{ secrets.GITHUB_TOKEN }} # automatically generated, no need to set
+        run: |
+          git config user.name "GH Action - Upstream Sync"
+          git config user.email "action@github.com"
 
-          # Set test_mode true to run tests instead of the true action!!
-          test_mode: false
+          git remote add upstream https://github.com/cmliu/edgetunnel.git
+          git fetch upstream main
 
-      - 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，详细教程请查看项目README.md "
-          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. Please refer to the project README.md for instructions. "
-          exit 1
+          if git diff --quiet HEAD upstream/main; then
+            # 内容和上游一致，直接对齐，顺带清理历史分叉留下的多余 merge commit
+            git reset --hard upstream/main
+            git push --force-with-lease origin main
+          else
+            # 有本地修改，保持原来的合并方式，不覆盖任何人的改动
+            git pull --no-rebase upstream main && git push origin main || {
+              echo "[Error] 合并上游变更产生冲突，自动同步已暂停，请手动 Sync Fork 并解决冲突。"
+              echo "[Error] Merge conflict detected while syncing upstream. Please sync your fork manually and resolve the conflicts."
+              exit 1
+            }
+          fi