.netlify.app or .vercel.app on your site's URL.git with the rest of the application software.package.json file at the repository root with a script specifying how to build the app. Then in Netlify, the deploy settings would need to be updated to reflect this change. 

package.json script first will cause the Netlify build to fail due to it being configured the old way. Updating the Netlify UI first will cause it's deploy to fail due to the code it's reading not supporting the new script yet.