Revert empty lfs ref name (#33454)

Fix #33453

modules/lfs/http_client.go

@@ -72,10 +72,14 @@ func (c *HTTPClient) batch(ctx context.Context, operation string, objects []Poin
 
 	url := fmt.Sprintf("%s/objects/batch", c.endpoint)
 
+	// Original:  In some lfs server implementations, they require the ref attribute. #32838
 	// `ref` is an "optional object describing the server ref that the objects belong to"
-	// but some (incorrect) lfs servers require it, so maybe adding an empty ref here doesn't break the correct ones.
+	// but some (incorrect) lfs servers like aliyun require it, so maybe adding an empty ref here doesn't break the correct ones.
 	// https://github.com/git-lfs/git-lfs/blob/a32a02b44bf8a511aa14f047627c49e1a7fd5021/docs/api/batch.md?plain=1#L37
-	request := &BatchRequest{operation, c.transferNames(), &Reference{}, objects}
+	//
+	// UPDATE: it can't use "empty ref" here because it breaks others like https://github.com/go-gitea/gitea/issues/33453
+	request := &BatchRequest{operation, c.transferNames(), nil, objects}
+
 	payload := new(bytes.Buffer)
 	err := json.NewEncoder(payload).Encode(request)
 	if err != nil {