Add an explicit distinction between a command's description and summary.

test/command_runner_test.dart

Index: test/command_runner_test.dart
diff --git a/test/command_runner_test.dart b/test/command_runner_test.dart
index bccc7b318d6ce6b9f631ec52be475eaff5ea0ab3..9961e7dc84e1d6b4df165e65d5021c6e34d4e4c8 100644
--- a/test/command_runner_test.dart
+++ b/test/command_runner_test.dart
@@ -54,7 +54,7 @@ Available commands:
 Run "test help <command>" for more information about a command."""));
     });
 
-    test("supports newlines in command descriptions", () {
+    test("truncates newlines in command descriptions by default", () {
       runner.addCommand(new MultilineCommand());
 
       expect(runner.usage, equals("""
@@ -68,6 +68,24 @@ Global options:
 Available commands:
   help        Display help information for test.
   multiline   Multi
+
+Run "test help <command>" for more information about a command."""));
+    });
+
+    test("supports newlines in command summaries", () {
+      runner.addCommand(new MultilineSummaryCommand());
+
+      expect(runner.usage, equals("""
+A test command runner.
+
+Usage: test <command> [arguments]
+
+Global options:
+-h, --help    Print this usage information.
+
+Available commands:
+  help        Display help information for test.
+  multiline   Multi
               line.
 
 Run "test help <command>" for more information about a command."""));