title: configure SourceMapDevToolPlugin to generate "source-map"
body: <p>TL;DR</p>
  
  <p>What config options do I need to set in the SourceMapDevToolPlugin to emulate <code>devtool: 'source-map'</code>?</p>
  
  <p>I <em>have</em> to use <code>SourceMapDevToolPlugin</code> to avoid generating a source map for my vendor modules....but I want <code>source-map</code> style maps, not <code>inline-source-map</code>.</p>
  
  <p>Details:</p>
  
  <p>I'm using webpack 4, and don't want to waste time generating a <code>vendor.js.map</code>, so I can't just set <code>devtool</code> and I instead do this:</p>
  
  <p><a href="https://webpack.js.org/plugins/source-map-dev-tool-plugin/#exclude-vendor-maps" rel="noreferrer">https://webpack.js.org/plugins/source-map-dev-tool-plugin/#exclude-vendor-maps</a></p>
  
  <p>but I notice this comment:</p>
  
  <blockquote>
    <p>You can use the following code to replace the configuration option devtool: inline-source-map with an equivalent custom plugin configuration:</p>
  </blockquote>
  
  <p>I, for the life of me, can't figure out what options I need to pass in to the plugin to replicate <code>devtool: 'source-map'</code>, instead of <code>inline-source-map</code></p>
  
  <p>my package.json:</p>
  
  <pre><code>"scripts": {
     "build": "webpack -p --config webpack.prod.js",
     "start": "webpack-dev-server --debug --bail --config webpack.dev.js"
  },
  </code></pre>
  
  <p>my (relavent) webpack config:</p>
  
  <pre><code>module.exports = {
     devtool: false, // using SourceMapDevToolPlugin instead
     optimization: {
       splitChunks: {
         cacheGroups: {
           commons: {
             test: /[\\/]node_modules[\\/]/,
             name: 'vendors',
             chunks: 'all'
           },
           styles: {
             test: /\.css$/,
             name: 'styles',
             chunks: 'all'
           }
        }
     },
     plugins: [
       new webpack.SourceMapDevToolPlugin({
         filename: '[name].map',
         exclude: ['vendor.js']
       })
     ]
  }
  </code></pre>
  
  <p>and my dev config:</p>
  
  <pre><code>module.exports = merge(common, {
    mode: 'development',
    devServer: {
      contentBase: './public',
      stats: 'minimal'
    }
  });
  </code></pre>
  
  <p>and my prod config</p>
  
  <pre><code>module.exports = merge(common, {
    mode: 'production',
    stats: 'errors-only'
  });
  </code></pre>