WordPress rename plugin main PHP file

old-plugin.php

<?php
/*
Plugin Name: Old Plugin main file
Description: Rename Old plugin main file (i.e. index.php) to `plugin-slug.php`
Version: 0.1.0
Author: Arūnas Liuiza
Author URI: http://arunas.co
License: GPL2
*/

add_action( 'admin_init', 'arunas_rename_plugin' );

function arunas_rename_plugin() {
	$old_plugin = plugin_basename( __FILE__ );
	$new_plugin = explode( '/', $old_plugin );
	$new_plugin = $new_plugin[0];
	$new_plugin = "{$new_plugin}/{$new_plugin}.php";
	deactivate_plugins( $old_plugin );
	activate_plugin( $new_plugin );
	unlink(__FILE__);
}