title: Git: show diff between branches, ignoring commits merged in
body: <p>My repository history looks something like this:</p>
  
  <pre><code>         x---y-+-z-+-branch
          /     /   /
  ---a---b---c-+-d-+-e---master
  </code></pre>
  
  <p>I want to get a single diff (i.e., like 'git diff' outputs- I don't want a whole bunch of diffs like 'git log -p' produces) of the complete history of 'branch', without including any of the changes that were merged into 'branch' from 'master'.</p>
  
  <p>How can I do this?</p>