Prevent WordPress theme update prompt

gistfile1.php

<?php
/**
 * Don't Update Theme
 * 
 * If there is a theme in the repo with the same name, 
 * this prevents WP from prompting an update.
 *
 * @author Mark Jaquith
 * @link http://markjaquith.wordpress.com/2009/12/14/excluding-your-plugin-or-theme-from-update-checks/
 * @since 1.0.0
 */
function ja_prevent_theme_update( $r, $url ) {
	if ( 0 !== strpos( $url, 'http://api.wordpress.org/themes/update-check' ) )
		return $r; // Not a theme update request. Bail immediately.
	$themes = unserialize( $r['body']['themes'] );
	unset( $themes[ get_option( 'template' ) ] );
	unset( $themes[ get_option( 'stylesheet' ) ] );
	$r['body']['themes'] = serialize( $themes );
	return $r;
}
add_filter( 'http_request_args', 'ja_prevent_theme_update', 5, 2 );