expand_sources

# File actionpack/lib/action_view/helpers/asset_tag_helpers/javascript_tag_helpers.rb, line 28
          def expand_sources(sources, recursive = false)
            if sources.include?(:all)
              all_asset_files = (collect_asset_files(custom_dir, ('**' if recursive), "*.#{extension}") - ['application']) << 'application'
              ((determine_source(:defaults, expansions).dup & all_asset_files) + all_asset_files).uniq
            else
              expanded_sources = sources.inject([]) do |list, source|
                determined_source = determine_source(source, expansions)
                update_source_list(list, determined_source)
              end
              add_application_js(expanded_sources, sources)
              expanded_sources
            end
          end