Stylesheet_link_tag, javascript_include_tag, caching problems

So, the new caching for stylesheet_link_tag, javascript_include_tag
which rolls up the files into one all.js or all.css files is great …
however I’ve run into an issue:

If all.cs or all.js don’t exist, they get generated … great, I’ve
reduced the number of gets …

The problem is what occurs when the files already exist … even if
I’ve changed my list of js/css files to something completely
different, it won’t rewrite the file if it already exists …

Do we really need the unless in this block? (asset_tag_helper.rb)

    def write_asset_file_contents(joined_asset_path, asset_paths)
      unless file_exist?(joined_asset_path)
        FileUtils.mkdir_p(File.dirname(joined_asset_path))
        File.open(joined_asset_path, "w+") { |cache|

cache.write(join_asset_file_contents(asset_paths)) }
end
end