module Roda::RodaPlugins::Assets::InstanceMethods

def asset_last_modified(file)

return the maximum.
other files, check the modification times of all dependencies and
Return when the file was last modified. If the file depends on any 
def asset_last_modified(file)
  if deps = self.class.assets_opts[:expanded_dependencies][file]
    ([file] + Array(deps)).map{|f| ::File.stat(f).mtime}.max
  else
    ::File.stat(file).mtime
  end
end