Don't truncate multi-line command descriptions.

test/utils.dart

Index: test/utils.dart
diff --git a/test/utils.dart b/test/utils.dart
index b6c6c717ace59f6cd6fccbb1d44eee104bf98600..3ef68873bd6e9934c521d01a0482e30045dbd4b9 100644
--- a/test/utils.dart
+++ b/test/utils.dart
@@ -27,6 +27,18 @@ class FooCommand extends Command {
   }
 }
 
+class MultilineCommand extends Command {
+  var hasRun = false;
+
+  final name = "multiline";
+  final description = "Multi\nline.";
+  final takesArguments = false;
+
+  void run() {
+    hasRun = true;
+  }
+}
+
 class HiddenCommand extends Command {
   var hasRun = false;