title: How to avoid composer discard changes message
body: <p>I'm updating symfony verdors via composer. I always do it using:</p>
  
  <pre><code>php composer.phar update
  </code></pre>
  
  <p>But recent version of composer, before update each package show a message like this:</p>
  
  <pre><code>  - Updating doctrine/data-fixtures dev-master (a95d783 =&gt; a28b6bd)
  The package has modified files:
  M .gitignore
  M .gitmodules
  M LICENSE
  M README.md
  M UPGRADE
  M composer.json
  M lib/Doctrine/Common/DataFixtures/AbstractFixture.php
  M lib/Doctrine/Common/DataFixtures/DependentFixtureInterface.php
  M lib/Doctrine/Common/DataFixtures/Event/Listener/MongoDBReferenceListener.php
  M lib/Doctrine/Common/DataFixtures/Event/Listener/ORMReferenceListener.php
  </code></pre>
  
  <p>-10 more files modified, choose "v" to view the full list
      Discard changes [y,n,v,s,?]? </p>
  
  <p>How to avoid this?</p>