> I would say only "datasources.php" and maybe "email.php".

In that case `email.php` should have been included in the ignore list which isn't :)

> Having those files gitignored helps when running cakephp/cakephp tests on our CI servers.

In 3.x core test don't use any config files from App. All required config is done through https://github.com/cakephp/cakephp/blob/3.0/lib/Cake/Test/init.php