Add a command-line option to set the exit code on a formatting change.

lib/src/debug.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /// Internal debugging utilities.
 library dart_style.src.debug;
 
 import 'dart:math' as math;
 
 import 'chunk.dart';
@@ skipping 68 matching lines @@
       if (chunk.isBlock) addSpans(chunk.block.chunks);
     }
   }
 
   addSpans(chunks);
 
   var spans = spanSet.toList();
   var rules =
       chunks.map((chunk) => chunk.rule).where((rule) => rule != null).toSet();
 
-  var rows = [];
+  var rows = <List<String>>[];
 
   addChunk(List<Chunk> chunks, String prefix, int index) {
-    var row = [];
+    var row = <String>[];
     row.add("$prefix$index:");
 
     var chunk = chunks[index];
     if (chunk.text.length > 70) {
       row.add(chunk.text.substring(0, 70));
     } else {
       row.add(chunk.text);
     }
 
     if (spans.length <= 20) {
@@ skipping 150 matching lines @@
 
       if (chunk.spaceWhenUnsplit) buffer.write(" ");
     }
   }
 
   buffer.write(chunks.last.text);
   log(buffer);
 }
 
 String _color(String ansiEscape) => useAnsiColors ? ansiEscape : "";