updated to webpack 4

build/version_plugin.js

@@ -0,0 +1,25 @@
+const commit = require('git-rev-sync').short();
+const pkg = require('../package.json');
+
+const version = JSON.stringify({
+  commit,
+  source: pkg.homepage,
+  version: process.env.CIRCLE_TAG || `v${pkg.version}`
+});
+
+class VersionPlugin {
+  apply(compiler) {
+    compiler.hooks.emit.tap('VersionPlugin', compilation => {
+      compilation.assets['version.json'] = {
+        source() {
+          return version;
+        },
+        size() {
+          return version.length
+        }
+      }
+    })
+  }
+}
+
+module.exports = VersionPlugin;