I tried to add this to the end of my wp-config.php
define('WP_CONTENT_DIR', $_SERVER['DOCUMENT_ROOT'] . '/somedir'); define('WP_CONTENT_URL', 'http://example.com/somedir');
however, echo immediately after that shows the old values (with wp-content value). I tried echo because in wp admin I couldn't see the theme from new location, of course.
I have installed wp in example.com/wp subdirectory and site itself is example.com - I copied over .htaccess and index.php over to the root and everything is working fine, I just need to move wp-content into another folder over at root also with a different name.