title: Join two git repos in a GNU stow like manner
body: <p>I have two git repositories with a few shared subdirectories between them, as shown below.</p>
  
  <pre><code>Repo 1                      Repo 2
  |-Folder A                  |-Folder A
  |  |-docA.c                 |  |-docX.c
  |-Folder B                  |-Folder B
  |  |-docB.c                 |  |-docY.c
  |-Folder C                  |-Folder D
  |  |-docC.c                 |  |-docZ.c
  </code></pre>
  
  <p>Now, I am trying to create a third repository that joins repo 2 into repo 1, in a GNU stow like manner. However, I would like to have the documents imported form repo 2 recognised as belonging to that repository, emulating the behaviour of git submodule. As far as I could figure out, submodule only lets me add an entire subfolder to my project form another repository. Just for reference, the third repository should have the following structure:</p>
  
  <pre><code>Repo 3
  |-Folder A
  |  |-docA.c
  |  |-docX.c
  |-Folder B
  |  |-docB.c
  |  |-docY.c
  |-Folder C
  |  |-docC.c
  |-Folder D
  |  |-docZ.c
  </code></pre>
  
  <p>Is this even possible to achieve? Or am I better off just keeping the two repositories separate, track their changes separately and using GNU stow when needed?</p>