title: Partial git repository merge
body: <p>I have been working a bit on a project I forked in GitHub. The source project I forked from was originally converted from a Mercurial project at Codeplex.</p>
  
  <p>Now I found out that someone else have been converting the Mercurial project into GitHub, but at a later stage and on top of that added some goodies in git.
  I would like to fork the other repo instead and replay my commits, since the other repo seems to be active. I also want to update the new repo with new changes in the original Mercurial repo.</p>
  
  <p>So here is the scenario:</p>
  
  <pre><code>My repo: 
  hg1-&gt;hg2-&gt;hg3-&gt;my1-&gt;my2
                 |
                 -&gt;my3
  hgN is the original Mercurial commits, myN is my git commits.
  
  Other guy:
  HG1-&gt;HG2-&gt;HG3-&gt;HG4-&gt;HG5-&gt;og1-&gt;og2
  HG1-HG3 are identical to hg1-hg3. Same file tree but with different hash though.
  ogN are git commits by that other guy.
  
  What I want:
  HG1-&gt;HG2-&gt;HG3-&gt;HG4-&gt;HG5-&gt;og1-&gt;og2
            |
            -&gt;my1-&gt;my2
              |
              -&gt;my3
  </code></pre>
  
  <p>Assuming I have cloned both repos and my changes include some branches, how would I create the merged repo?</p>
  
  <p>What if I my changes was in a single branch. Could I do a simple rebase then?</p>