Use custom sourcemap file names

packages/react-scripts/config/webpack.config.dev.js

@@ -11,6 +11,7 @@
 'use strict';
 
 const autoprefixer = require('autoprefixer');
+const path = require('path');
 const webpack = require('webpack');
 const HtmlWebpackPlugin = require('html-webpack-plugin');
 const CaseSensitivePathsPlugin = require('case-sensitive-paths-webpack-plugin');
@@ -72,6 +73,9 @@ module.exports = {
     filename: 'static/js/bundle.js',
     // This is the URL that app is served from. We use "/" in development.
     publicPath: publicPath,
+    // Point sourcemap entries to original disk location
+    devtoolModuleFilenameTemplate: info =>
+      path.relative(paths.appSrc, info.absoluteResourcePath),
   },
   resolve: {
     // This allows you to set a fallback for where Webpack should look for modules.