title: Composer dont init and update submodules
body: <p>I'm making a composer library that have the following structure</p>
  
  <pre><code>- vendor/
  - src/
  - data/
      - cnab/ (Submodule: contains files that can be reused in other projects)
  - composer.json
  </code></pre>
  
  <p>However when I require my library in other project, submodules are not started and updated. </p>
  
  <p>I tried to use composer scripts but no success:</p>
  
  <pre><code>"scripts": {
      "post-install-cmd": [
          "git submodule init",
          "git submodule update"
      ]
  }
  </code></pre>