Fixes #8 - Adds build number to env vars

Author: JamieDixon

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

@@ -266,6 +266,10 @@ module.exports = {
     // if (process.env.NODE_ENV === 'development') { ... }. See `./env.js`.
     new webpack.DefinePlugin(
       Object.assign({}, env.stringified, {
+        // Currently builds may run in both travis and jenkins env
+        'process.env.BUILD_NUMBER': JSON.stringify(
+          process.env.TRAVIS_BUILD_NUMBER || process.env.BUILD_NUMBER || '----'
+        ),
         'process.locales': JSON.stringify(locales),
       })
     ),

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

@@ -309,6 +309,9 @@ module.exports = {
     // Otherwise React will be compiled in the very slow development mode.
     new webpack.DefinePlugin(
       Object.assign({}, env.stringified, {
+        'process.env.BUILD_NUMBER': JSON.stringify(
+          process.env.TRAVIS_BUILD_NUMBER || process.env.BUILD_NUMBER || '----'
+        ),
         'process.locales': JSON.stringify(locales),
       })
     ),