anchor.diff:  part of aqueduct;
  -
  -class MigrationConfiguration extends ConfigurationItem {
  -  MigrationConfiguration(String filename) : super.fromFile(filename);
  -
  -  DatabaseConnectionConfiguration migration;
  -}
   
   class MigrationRunner extends CLICommand {
     MigrationExecutor executor;
  
positive.code:     ..addCommand("list-versions")
      ..addCommand("version")
      ..addFlag("help", negatable: false, help: "Shows this documentation");
  
  
    Future<int> handle(ArgResults argValues) async {
  
negative.code: 
      PersistentStore store = null;
      if (argValues["flavor"] == "postgres") {
        var dbConfigFile = new File.fromUri(dbConfigURI);
        if (dbConfigFile.existsSync()) {
          var dbConfig = new DatabaseConnectionConfiguration();
          try {
            dbConfig.readFromMap(loadYaml(dbConfigFile.readAsStringSync()) as Map<String, dynamic>);
          } catch (e) {
            print("Invalid dbconfig. Expected $_dbConfigFormat\nat ${dbConfigURI}.");
            rethrow;
          }
          store = new PostgreSQLPersistentStore.fromConnectionInfo(dbConfig.username, dbConfig.password, dbConfig.host, dbConfig.port, dbConfig.databaseName);
        }
      } else {
  