title: Git diff with remote tag
body: <p>I'm about to merge a big change from a remote branch (non-origin), and more specifically from a given tag.</p>
  
  <p>There are two remotes then:</p>
  
  <ol>
  <li><code>origin</code></li>
  <li><code>proposal</code></li>
  </ol>
  
  <p>On the <code>proposal</code> remote, a branch name <code>idea</code> exists, with a tag <code>tagged_idea</code>.</p>
  
  <p>The idea is that I want to review the incoming changes between <code>tagged_idea</code> and my current HEAD. How can I achieve this?</p>
  
  <p>I tried something like <code>git diff .../proposal/tags/tagged_idea</code> but it didn't work well. Any idea?</p>
  
  <p>In other terms, what I would like to see is the result of the merge, before even doing it in my branch. Just like if I did the pull <code>git pull proposal tags/tagged_idea</code> but without actually making the changes.</p>