expand_javascript_sources

# File actionpack/lib/action_view/helpers/asset_tag_helper.rb, line 635
        def expand_javascript_sources(sources, recursive = false)
          if sources.include?(:all)
            all_javascript_files = collect_asset_files(JAVASCRIPTS_DIR, ('**' if recursive), '*.js')
            ((determine_source(:defaults, @@javascript_expansions).dup & all_javascript_files) + all_javascript_files).uniq
          else
            expanded_sources = sources.collect do |source|
              determine_source(source, @@javascript_expansions)
            end.flatten
            expanded_sources << "application" if sources.include?(:defaults) && File.exist?(File.join(JAVASCRIPTS_DIR, "application.js"))
            expanded_sources
          end
        end