title: Avoid re-entering password for each submodule
body: <p>I have a repo with 3 submodules. The repo and submodules are all on the same server, which I have ssh access to. The remote URLs are:</p>
  
  <pre><code>ssh://mm@theserver.com/path/to/sub1.git
  ssh://mm@theserver.com/path/to/sub2.git
  ssh://mm@theserver.com/path/to/sub3.git
  </code></pre>
  
  <p>If I do an operation such as <code>git submodule update --remote</code> then it prompts for my password 3 times.</p>
  
  <p>Is there any way to update the submodules but only require password once?  Same goes for committing changes etc.</p>