Link to dartlang.org in pub's command-line help messages.

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

Index: sdk/lib/_internal/pub/lib/src/command.dart
diff --git a/sdk/lib/_internal/pub/lib/src/command.dart b/sdk/lib/_internal/pub/lib/src/command.dart
index 1765c108aad97d816a8ad2485f27bf822159e037..ddf6f30331da4a3f5ff353d7bb2e6d91f3790612 100644
--- a/sdk/lib/_internal/pub/lib/src/command.dart
+++ b/sdk/lib/_internal/pub/lib/src/command.dart
@@ -56,6 +56,8 @@ abstract class PubCommand {
     buffer.writeln();
     buffer.writeln(
         'Use "pub help [command]" for more information about a command.');
+    buffer.writeln(
+        'See http://dartlang.org/tools/pub for detailed documentation.');
 
     log.message(buffer);
   }
@@ -119,6 +121,9 @@ abstract class PubCommand {
   /// How to invoke this command (e.g. `"pub get [package]"`).
   String get usage;
 
+  /// The URL for web documentation for this command.
+  String get docUrl => null;
+
   /// Whether or not this command requires [entrypoint] to be defined.
   ///
   /// If false, pub won't look for a pubspec and [entrypoint] will be null when
@@ -244,6 +249,11 @@ abstract class PubCommand {
       buffer.write(_listCommands(subcommands));
     }
 
+    if (docUrl != null) {
+      buffer.writeln();
+      buffer.writeln("See $docUrl for detailed documentation.");
+    }
+
     return buffer.toString();
   }
 }