grpc: watch metadata changes by directory

weed/pb/master_pb/master.pb.go

@@ -1611,7 +1611,9 @@ func (x *StatisticsResponse) GetFileCount() uint64 {
 	return 0
 }
 
+//
 // collection related
+//
 type Collection struct {
 	state         protoimpl.MessageState
 	sizeCache     protoimpl.SizeCache
@@ -1846,7 +1848,9 @@ func (*CollectionDeleteResponse) Descriptor() ([]byte, []int) {
 	return file_master_proto_rawDescGZIP(), []int{23}
 }
 
+//
 // volume related
+//
 type DiskInfo struct {
 	state         protoimpl.MessageState
 	sizeCache     protoimpl.SizeCache