indeed, if we are going to remove everything in public/assets on assets:clean, just do that

actionpack/lib/sprockets/assets.rake

@@ -17,9 +17,6 @@ namespace :assets do
   task :clean => :environment do
     assets = Rails.application.config.assets
     public_asset_path = Rails.public_path + assets.prefix
-    file_list = FileList.new("#{public_asset_path}/**/*")
-    file_list.each do |file|
-      rm_rf file
-    end
+    rm_rf public_asset_path, :secure => true
   end
 end