Add destroy to engine's commands

railties/lib/rails/engine/commands.rb

@@ -13,10 +13,10 @@ require ENGINE_PATH
 engine = ::Rails::Engine.find(ENGINE_ROOT)
 
 case command
-when 'generate'
+when 'generate', 'destroy'
   require 'rails/generators'
   engine.load_generators
-  require 'rails/commands/generate'
+  require "rails/commands/#{command}"
 
 when '--version', '-v'
   ARGV.unshift '--version'
@@ -29,6 +29,7 @@ Usage: rails COMMAND [ARGS]
 
 The common rails commands available for engines are:
  generate    Generate new code (short-cut alias: "g")
+ destroy     Undo code generated with "generate"
 
 All commands can be run with -h for more information.
   EOT