title: Apt-get does not find package `git` on Ubuntu 12.04
body: <p>I am trying to install git on ubuntu 12.04. But when enter the command</p>
  
  <pre><code>sudo apt-get install git
  </code></pre>
  
  <p>I get the following message. I have run <code>sudo apt-get update</code> already.</p>
  
  <pre><code>Reading package lists... Done
  Building dependency tree       
  Reading state information... Done
  Package git is not available, but is referred to by another package.
  This may mean that the package is missing, has been obsoleted, or
  is only available from another source
  However the following packages replace it:
    git-el
  
  E: Package 'git' has no installation candidate
  </code></pre>