title: Get submodule hash from bare repository
body: <p>We have a gitolite server with our customers custom apps.</p>
  
  <p>Every app has a submodule "repository/core" which refers to our base app.</p>
  
  <p>We would now like to create a dashboard which shows all our customers apps and at which revision there core is at.</p>
  
  <p>gitolite stores everything in bare repositories on disk and the dashboard app has direct access to the repos / or using ssh keys if that's easier.</p>
  
  <p>My question is how would I from a bare repository find out what revision a submodule is at, and who committed it?</p>