title: Using git with sources which are provided as a tarball
body: <p>The scenario is this:</p>
  
  <ul>
  <li>Some provider provides source code in tgz format. I have no access to their repositories.</li>
  <li>I opened the sources, and created a local git repository with the sources.</li>
  <li>I do changes to the sources, and commit them to my git.</li>
  <li>Now the provider provides a new version of the source code.</li>
  <li>I want to merge the new code in my git repositories.</li>
  </ul>
  
  <p>Is this possible?</p>
  
  <p>(I cannot ask the provider to provide the source in other means)</p>
  
  <p>Thank you</p>