title: How do I build with watch enabled using angular-cli?
body: <p>I don't want to use serve, I know it watches for changes, builds and serves.
  I want to build upon changes.
  According to "ng help", build takes parameter --watch</p>
  
  <blockquote>
    <p>ng build    Builds your app and places it into the output
    path (dist/ by default).
    --watch (Boolean) (Default: false)
        aliases: -w   --watcher (String)</p>
  </blockquote>
  
  <p>I tried both -w and --watcher but it just gives error.</p>
  
  <pre><code>&gt;ng build -w
  
  Path must be a string. Received null
  </code></pre>