title: Importing as sub-tree a public repo containing sub-modules
body: <p>For customizing a firmware (FW) from a github repository (which uses git-submodules), I was planning to 'import' this public repository as a git-subtree in my own repository.</p>
  
  <p>In theory, I will never have to modify the original FW code but just make additions to an external folder that will be used during compilation.</p>
  
  <p>I am fairly new to git but git-subtree seems convenient for grouping the original FW with the new content in a single repository, while 'freezing' the FW to a version (commit) compatible with the added scripts/configs.</p>
  
  <p>Interestingly, the original FW repository contains mostly git-submodules and I don't know if I will be able to manage this nested situation (git-submodules inside a git-subtree).</p>
  
  <p>If I do:</p>
  
  <pre><code>git subtree add --prefix officialFW https://github.com/analogdevicesinc/plutosdr-fw.git master --squash
  </code></pre>
  
  <p>I believe that the submodules content is not retrieved as when I make a <code>git clone --recurse-submodules</code>.<br>
  Should I <code>git pull</code> them manually afterwards ?</p>
  
  <p>Any help on how to get that done is appreciated.</p>
  
  <p>I would also appreciate comments on the sub-tree strategy for my use-case, or remarks about using them in this specific context (with nested submodules, should we avoid mixing them ?).</p>
  
  <p>Thank you.</p>