title: Combine add git repository one repo as branches
body: <p>I have two directories, each their own git repo, that I have realized are two parts/versions of the same project.  I'd like to add them as sub-directories to a new project folder, while preserving the commit history of each. </p>
  
  <p>Ideally, project_A and project_B would be branches of the same parent git repository.</p>
  
  <p>Existing file structure:</p>
  
  <pre><code>project_A
  | --.git
  | --project_B files
  
  project_B
  | --.git
  | --project_B files
  </code></pre>
  
  <p>Taraget File Structure:</p>
  
  <pre><code>ParentProjectFolder
  |--project_A
  |   | --project_A files
  |--project_B
  |   | --project_B files
  </code></pre>
  
  <p>Can this be done?</p>