class Sprockets::DirectiveProcessor

*/
*= require_tree .
*= require_self
/*= require "reset"

be defined before other dependencies are loaded.
it's common for the index file to contain global styles that need to
before any subsequent `require` directives. Useful in CSS files, where
`require_self` causes the body of the current file to be inserted

def process_require_self_directive
  if @required.include?(@uri)
    raise ArgumentError, "require_self can only be called once per source file"
  end
  @required << @uri
end