title: Configure environment for React Native / Fastlane app
body: <p>I have a <a href="https://facebook.github.io/react-native/" rel="nofollow noreferrer">React Native</a> app (iOS and Android) that I need to build for two clients. I want to replace the logo and colours of the app at build time.</p>
  
  <p>Some options I've considered:</p>
  
  <ul>
  <li>Branch/fork the repository. Problem: more work to maintain two versions.</li>
  <li>Keep assets outside of source tree to be provided at build time. Problem: trickier to set up, especially with CI (?)</li>
  <li>Check all assets in and switch between them with an environment variable. Problem: don't know how to set environment variable when app runs on the device. Also it's not scalable, but for now that's OK.</li>
  </ul>
  
  <p>How can I parameterise a React Native app, particularly one deployed with <a href="https://fabric.io/features/distribution" rel="nofollow noreferrer">Fastlane</a>? .. maybe by passing parameters <a href="https://docs.fastlane.tools/advanced/#passing-parameters" rel="nofollow noreferrer">like this</a>?</p>