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

lib/src/debug.dart

Index: lib/src/debug.dart
diff --git a/lib/src/debug.dart b/lib/src/debug.dart
index 55734cfa6782e6f0a37165f3873a0a48c994d6c4..b3ca65fc13aa6c6132c4e91e1145c61dd5867f86 100644
--- a/lib/src/debug.dart
+++ b/lib/src/debug.dart
@@ -86,10 +86,10 @@ void dumpChunks(int start, List<Chunk> chunks) {
   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];