fix diff generation and add test coverage

base/src/test/user_model/mod.rs

@@ -1,6 +1,7 @@
 mod test_add_delete_sheets;
 mod test_autofill_columns;
 mod test_autofill_rows;
+mod test_batch_row_column_diff;
 mod test_border;
 mod test_clear_cells;
 mod test_column_style;