anchor.diff:      exitCode = 1;
       return;
     }
  +  Set<String> namedConfigurations = configurations.configurationNames;
     // Print information about the resolved builders to compare with.
     for (final builder in configurations.builders) {
       if (localConfiguration != null) {
  
positive.code:       branches,
        buildersConfigurations,
        options["branch"],
        namedConfigurations,
        requestedBuilder);
    if (configurations == null) {
      // No valid configuration could be found. The error has already been
  
negative.code:   }
  
    final requestedBuilder = options["builder"];
    final requestedNamedConfigurations =
        (options["named-configuration"] as List).cast<String>();
    final localConfiguration = options["local-configuration"] as String;
  
    if (requestedBuilder == null && requestedNamedConfigurations.isEmpty) {
      printUsage(parser,
          error: "Please specify either a configuration (-n) or "
              "a builder (-b)");
      return;
    }
  
    if (localConfiguration != null && requestedNamedConfigurations.length > 1) {
      printUsage(parser,
          error: "Local configuration (-N) can only be used with a"
              " single named configuration (-n)");
  