title: git: generate a single patch across multiple commits
body: <p>This is the situation:</p>
  
  <ol>
  <li><p>We created a "private" repo (say our-repo) based off an existing open-source git repo (say source-repo).</p></li>
  <li><p>We have been developing code and have around 20 merges into our repo. So, the repo moved from "State_Initial" to "State_Current".</p></li>
  </ol>
  
  <p>Now, for business reasons, we want to hand-over all our development to a third party. Based on some legal issues, the only option is we give them a "single" patch file with all our changes. That is a squashed patch between "State_Initial" and "State_Current".</p>
  
  <p>I looked around, and found </p>
  
  <pre><code>git format-patch -X
  </code></pre>
  
  <p>But, it generates "n" .patch files.</p>
  
  <p>Is there a way to create a single patch file, so that if we create a repo based off "source-repo" and apply the patch, it takes us to "State_Current"?</p>