title: git asks to commit submodule modified content
body: <p>Recently I updated submodules in my vim configuration repository with this command:</p>
  
  <pre><code>git submodule update --recursive --remote
  </code></pre>
  
  <p>And when I called <code>git status</code> I got this:</p>
  
  <pre><code>On branch master
  Your branch is ahead of 'origin/master' by 5 commits.
    (use "git push" to publish your local commits)
  Changes not staged for commit:
    (use "git add &lt;file&gt;..." to update what will be committed)
    (use "git checkout -- &lt;file&gt;..." to discard changes in working directory)
    (commit or discard the untracked or modified content in submodules)
  
          modified:   .vim/pack/starter-pack/start/YouCompleteMe (modified content)
  
  no changes added to commit (use "git add" and/or "git commit -a")
  </code></pre>
  
  <p>Then I followed the chain of submodules that have "modified content" and found that the only modification was the untracked commits of submodules:</p>
  
  <pre><code>On branch master
  Your branch is behind 'origin/master' by 1 commit, and can be fast-forwarded.
    (use "git pull" to update your local branch)
  Changes not staged for commit:
    (use "git add &lt;file&gt;..." to update what will be committed)
    (use "git checkout -- &lt;file&gt;..." to discard changes in working directory)
  
          modified:   vendor/bottle (new commits)
          modified:   vendor/jedi (new commits)
          modified:   vendor/waitress (new commits)
  
  no changes added to commit (use "git add" and/or "git commit -a")
  </code></pre>
  
  <p>master branches of these submodules (bottle, jedi, waitress) are behind master branches of their remote origins, so I suppose what <code>git submodule update</code> did is not just pull origins of each repo, but find appropriate version that parent repository requires.</p>
  
  <p>Why even git marks this repos with <code>(new commits)</code> if it is exact commits that parent modules require? What is going on there?</p>