Config files that are not version controlled, or environment variables. I prefer config files because it's easier for me to communicate to other team members wh

Config files that are not version controlled, or environment variables. I prefer config files because it's easier for me to communicate to other team members what needs to be present in their local development environment. I typically handle this by versioning a `config.example` file, which includes all the necessary config keys an application expects. The example file defaults these attrs to various strings meant to show they are examples only. I include instructions to copy the `config.example` to a `config.yml` (or some other appropriate extension), and replace the values as necessary. The `config.yml` file is specifically excluded in the `.gitignore` file. The application will only load the `config.yml` file when started, so I also ensure to raise a descriptive error informing team members when they are missing a local `config.yml`. This allows the `config.example` to also serve as a self-documenting config for the application, as comments can be included that identify and explain each of the config keys and their purposes.