Dotenv file custom path/env

[Xerphis]

Is your proposal related to a problem?

Standard support for environment files is limited to reading defined paths (https://github.com/bkeepers/dotenv#what-other-env-files-can-i-use); Therefore, it is impossible to define what environment file we want to use when building a project for non-end users build, but for example, staging/demo.

Describe the solution you'd like

Allow the definition of an additional pre-production environment by setting an env variable (eg. DOTENV_CUSTOM_ENV) or an argument for npm run buld --staging/demo. In the following order or otherwise:
react-scripts/config/env.js

// https://github.com/bkeepers/dotenv#what-other-env-files-can-i-use
const dotenvFiles = [
	`${paths.dotenv}.${NODE_ENV}.local`,
	// Don't include `.env.local` for `test` environment
	// since normally you expect tests to produce the same
	// results for everyone
	NODE_ENV !== "test" && `${paths.dotenv}.local`,
	`${paths.dotenv}.${process.env.DOTENV_CUSTOM_ENV}`,
	`${paths.dotenv}.${NODE_ENV}`,
	paths.dotenv,
].filter(Boolean);

With this solution, running a script by "DOTENB_CUSTOM_ENV=staging npm run build", react-scripts reads the file .env.staging

Describe alternatives you've considered

An alternative solution would be to allow set the full path to the .env file. This method would point to an environment file that could be used by many different projects.

[ryanberckmans]

I would like this feature, too.

I want to run create-react-app's production build, but using a staging dotenv file. This allows me to deploy a minified production build that customers may test against test-mode dependencies, eg test.myapp.com. It's also helpful for a demo mode where I want to showcase functionality to customers against test data.