Make javascript_include_tag :default behave correctly with application.js, fixes #2986

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@3164 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

actionpack/lib/action_view/helpers/asset_tag_helper.rb

@@ -60,7 +60,7 @@ def javascript_path(source)
       def javascript_include_tag(*sources)
         options = sources.last.is_a?(Hash) ? sources.pop.stringify_keys : { }
         if sources.first == :defaults
-          sources = @@javascript_default_sources
+          sources = @@javascript_default_sources.dup
           if defined?(RAILS_ROOT) and File.exists?("#{RAILS_ROOT}/public/javascripts/application.js")
             sources << 'application' 
           end