title: Is there a way to automatically generate `Imports` section in the DESCRIPTION file?
body: <p>When developing an R package, it is common for me to just turn on Packrat and use a localized repository, and develop as I explore in a session. But when publishing the package, it is a big headache to recall and manually add every dependency I have used in the developed package. Is there a (semi-)automatic way to do this?</p>
  
  <p>For example, in NodeJS development, we can just use <code>npm install --save</code> and the dependency will be added automatically to <code>package.json</code>.</p>