title: Get the current commit id of specified submodule
body: <p>I want get the current commit id of the specified submodule. I thought when I cd into submodule directory and run <code>git rev-parse HEAD</code> i get this after I noticed this is a superproject current id.
  Tried <code>git submodule status | grep &lt;submodule_name&gt;</code> also but its to slow to me. Any idea how to get this information little bit faster?</p>