webpack.base.config.js

// apps/other/client/webpack/webpack.base.config.js

const Config = require('webpack-config').default;
const environment = require('webpack-config').environment;
const path = require('path');

const key = environment.valueOf('projectKey');
const main = environment.valueOf(key);

module.exports = new Config().merge({
  entry: {
    main  : `${main.appPath}/startup/App`,
  },
  output: {
    filename     : main.outputFilename,
    chunkFilename: main.outputChunkFilename,
    path         : path.resolve(main.dirname, main.outputPath),
    publicPath   : main.outputPublicPath,
  },
});

webpack.config.js

// apps/main/client/webpack.config.js
const Config = require('webpack-config').default;
const environment = require('webpack-config').environment;

const data = {
    env,
    isProd,
    projectKey    : env.projectKey || 'sub',
    webpackConfigs: '../../other/client/webpack',
    main          : {
      dirname: __dirname,
      packages,
      appPath, /* string */
    },
  };

  environment.setAll(data);

const config = new Config().extend('[webpackConfigs]/webpack.base.config.js');