anchor.diff:  main(List<String> args) async {
     var parser = new ArgParser();
   
  -  parser.addOption("target", abbr: "t", defaultsTo: "browser", allowed: ["browser", "node"]);
  +  parser.addOption("target",
  +      abbr: "t", defaultsTo: "browser", allowed: ["browser", "node"]);
     parser.addOption("file", abbr: "f");
     parser.addOption("wrapper", abbr: "w");
   
  -  if(args.length == 0) {
  +  if (args.length == 0) {
       print(parser.usage);
       return;
     }
  
positive.code: 
    List<String> data = file.readAsLinesSync();
  
    if(results["target"] == "node") {
      // node preamble
      data.insert(0, """
      global.location = { href: "file://" + process.cwd() + "/" };
  
negative.code:   }
  
    var index = data.length;
    for (var line in data.reversed) {
      index--;
      if (line.contains("// END invoke [main].")) {
        data.insertAll(index, new File(results["wrapper"]).readAsLinesSync());
        continue;
      }
  
      if (line.contains("main: [function(args) {")) {
        data.removeRange(index + 1, index + 4);
        break;
      }
    }
  
  