title: where the links to previous versions of file are located in git
body: <p>In Git book there is a phrase</p>
  
  <p>"To be efficient, if files have not changed, Git doesn’t store the file again—just a link to the previous identical file it has already stored"</p>
  
  <p>So all the git object are stored in the folder <code>.git\objects</code>. And when I commit - it adds folder for new commit and the folders for all new files(folder name - first two symbols of hash code as far as I can see).</p>
  
  <p>But the question is - how git operates with not changed files? where are the references/link kept in git repository? I mean how does <code>commit</code> knows that it should reference to a certain not changed file?</p>