Git is not tracking my config/database.php

I am a newbie in LARAVEL but i can say that this is so cool. As of now i tried to deploy my first app in heroku the first time i did is it work fine but last day i tried to add some new functionalities and try to deploy it once again, and when i type the "php artisan migrate" command in heroku it shows an error that as far i i know is connected to my congfig/database.php file.

After some hours of debugging i found out that my config/database.php file is not track by git it is so weird because i did not specify that directory in my .gitignore file.