title: grunt, grunt-shell - command inheritance
body: <p>I need something like command inheritance like this:</p>
  
  <pre><code>shell:
      virtualenvActivate:
          command: [
              '. `command -v virtualenvwrapper.sh`'
              'workon &lt;%= pkg.name %&gt;'
          ].join '&amp;&amp;'
      pelican:
          command: [
              shell:virtualenvActivate # &lt;-- THIS LINE
              'pelican src/content/ -o dist/ -s publishconf.py'
          ].join '&amp;&amp;'
  </code></pre>
  
  <p>Is it ever possible?</p>