anchor.diff:    buildInputs = [ getopt netcat ]
       ++ lib.optional stdenv.isLinux systemd
       ++ lib.optional enableEjabberdDump ejabberd
  -    ++ lib.optional enableMySQLDatabase mysql.out
  +    ++ lib.optional enableMySQLDatabase mariadb.out
       ++ lib.optional enablePostgreSQLDatabase postgresql
       ++ lib.optional enableSubversionRepository subversion
       ++ lib.optionals enableMongoDatabase [ mongodb mongodb-tools ]
  
positive.code: { lib, stdenv, fetchurl, netcat
  
  # Optional packages
  , systemd ? null, ejabberd ? null, mysql ? null, postgresql ? null, subversion ? null
  , mongodb ? null, mongodb-tools ? null, influxdb ? null, supervisor ? null, docker ? null
  , nginx ? null, s6-rc ? null, xinetd ? null
  
  
negative.code: , getopt
  }:
  
  assert enableMySQLDatabase -> mariadb != null;
  assert enablePostgreSQLDatabase -> postgresql != null;
  assert enableSubversionRepository -> subversion != null;
  assert enableEjabberdDump -> ejabberd != null;
  