add repeat()

prettyjson.dart

@@ -9,16 +9,18 @@ main(List<String> args) async {
     return;
   }
   final restArgs = parseResult.rest;
+  final width = int.parse(parseResult['width']);
 
   final jsonContent = await readContent(restArgs);
   final jsonDecoded = json.decode(jsonContent);
-  JsonEncoder encoder = new JsonEncoder.withIndent('    ');
+  JsonEncoder encoder = new JsonEncoder.withIndent(repeat(' ', width));
   print(encoder.convert(jsonDecoded));
 }
 
 ArgResults parseArgs(List<String> args) {
   final parser = new ArgParser();
   parser.addFlag('help', abbr: 'h', defaultsTo: false, help: 'Help');
+  parser.addOption('width', abbr: 'w', defaultsTo: '4', help: 'Space width');
 
   return parser.parse(args);
 }
@@ -40,6 +42,14 @@ Future<String> readFromStdin() async {
     return Future<String>.value(stdinContentArray.join('\n'));
 }
 
+String repeat(String s, int count) {
+  var ret = '';
+  for (var i = 0; i < count; i++) {
+    ret += s;
+  }
+  return ret;
+}
+
 printHelp() {
   print('pretty.dart - version 0.1');
   print('Usage:');