Custom login template

Working on a new templating system and trying to figure out how to make the wp-login.php load a custom file in my theme directory.

wp-content/themes/custom/login.php

How should I go about doing this? I read the Codex page on how to custom style the login page but its sloppy.

http://codex.wordpress.org/Customizing_the_Login_Form

I’d prefer to custom code my own page.