title: Why does "git submodule add ..." write to stderr rather than stdout?
body: <p>The message</p>
  
  <pre><code>Cloning into 'sub-mod'...
  done.
  </code></pre>
  
  <p>after a <code>git submodule add...</code> command is written to <em>stderr</em>. I expected the message to be written to <em>stdout</em> since I don't think it indicates something went wrong with the command.</p>
  
  <p>I can reproduce this with the following sequence of commands:</p>
  
  <pre><code>rm   -rf /tmp/repo /tmp/module
  mkdir    /tmp/repo /tmp/module
  
  cd /tmp/module
  
  git init  &gt; /dev/null
  echo "foo" &gt; foo;
  git add foo &gt; /dev/null
  git commit . -m "+ foo" &gt; /dev/null
  
  
  cd /tmp/repo
  
  git init &gt; /dev/null
  git submodule add /tmp/module/ sub-mod 1&gt; /dev/null
  </code></pre>
  
  <p>If I change the redirection in the last command to <code>... 2&gt; /dev/null</code>, nothing is printed.</p>