According to the magento 2 upgrade to 2.1.7 to 2.2 they highlighted "config.local.php" file. I cant find it, can anyone know where is it ? http://devdocs.magento.com/guides/v2.2/cloud/project/project-upgrade.html
This information details how to upgrade Magento Commerce (Cloud) to 2.2.X from any version, and upgrading to new 2.2.X versions.
Note: Only Magento Commerce (Cloud), not for CE or EE.
you can find this file in following folders:
Hope it will help you! Thanks