title: can't add git submodule to repository
body: <p><em>(Predominantly a Git question, but may be relevant to other PyroCMS users)</em></p>
  
  <p>I have a local repository of PyroCMS - the repo is a clone of a github fork of the main project.  I also have a PyroCMS module, which is also a local clone of a github fork of <em>that</em> project.  </p>
  
  <p>I've put them both in separate directories.</p>
  
  <pre><code>~/Dropbox/websites/pyrocmscommunity-test/
  ~/Dropbox/github/PyroDatabase/
  </code></pre>
  
  <p>I want to add PyroDatabase as a <strong>submodule</strong> of pyrocmscommunity-test, so I can pull updates from github, keep track of my own changes etc.</p>
  
  <p>I tried to do this by going to the top of the working tree and doing:</p>
  
  <pre><code>git submodule add ../../github/PyroDatabase/ addons/shared_addons/modules/
  </code></pre>
  
  <p>but it didn't complete properly:</p>
  
  <pre><code>Cloning into 'addons/shared_addons/modules/database'...
  ssh_exchange_identification: Connection closed by remote host
  fatal: The remote end hung up unexpectedly
  </code></pre>
  
  <p>I don't understand this as I didn't specify an SSH connection, I just wanted to use the local repo.  What is it trying to connect to and why?</p>
  
  <p>Also, now, whenever I repeat the command, I get this:</p>
  
  <pre><code>'addons/shared_addons/modules' already exists in the index
  </code></pre>
  
  <p>But I don't understand this as there is no <code>.gitmodules</code> file and no mention of the modules files in <code>.gitconfig</code> either.  </p>
  
  <p>What am I doing wrong and how do I reset things?</p>
  
  <p>Thanks,
  William</p>