Support subcommands in pub and pub help.

sdk/lib/_internal/pub/lib/src/log.dart

Index: sdk/lib/_internal/pub/lib/src/log.dart
diff --git a/sdk/lib/_internal/pub/lib/src/log.dart b/sdk/lib/_internal/pub/lib/src/log.dart
index bbbcb3c95f5bcf6250c0bb6a50276778c4303e1c..6999cb9eacb2ee9b0d849f57eafed5d2a40b011c 100644
--- a/sdk/lib/_internal/pub/lib/src/log.dart
+++ b/sdk/lib/_internal/pub/lib/src/log.dart
@@ -117,6 +117,13 @@ void write(Level level, message) {
   if (_loggers.isEmpty) showNormal();
 
   var lines = splitLines(message.toString());
+
+  // Discard a trailing newline. This is useful since StringBuffers often end
+  // up with an extra newline at the end from using [writeln].
+  if (lines.isNotEmpty && lines.last == "") {
+    lines.removeLast();
+  }
+
   var entry = new Entry(level, lines);
 
   var logFn = _loggers[level];