.gitignore file for CodeIgniter 3

https://github.com/bcit-ci/CodeIgniter has its own .gitignore file, which is more appropriate.

A good practice is to keep the framework (the above project) separate from any app, and to reference its system folder location in your app's index.php. You can then share the framework across apps, and update the framework without affecting your apps.

What you are referring to in your post is the .gitignore file from the github repositories, presumably a default one.
Check the .gitignore in our project.