title: Merge new branch with uncorrelated history into repository subdirectory using Git
body: <p>There are 2 branches in a repository: master and my_branch. my_branch is newly pushed branch with contents from another repository and uncorrelated history. I would like to merge my_branch into master, however:</p>
  <pre><code>git checkout master
  git merge master my_branch
  </code></pre>
  <p>would merge them on the root level which is not what I want.</p>
  <p>I would like to merge the root directory contents of my_branch with subdirectory of the root directory of master.</p>
  <p>Would anyone be able to advise me on how to proceed on this?</p>