title: How Composer handles local changes
body: <p>Suppose I install <a href="https://github.com/2amigos/yii2-editable-widget" rel="nofollow noreferrer">package for CKEditor</a> through Composer and manually <a href="https://github.com/2amigos/yii2-ckeditor-widget#skins--plugins" rel="nofollow noreferrer">add new skins and plugins to it</a>. How Composer will handle this, when next update to base package will be released? </p>
  
  <p>Will it overwrite entire package directory (deleting local changes) or update only listed files?</p>
  
  <p>Also, <a href="https://stackoverflow.com/q/29532260/1469208">I'm having problems updating one package to newest version</a> and made that update locally, manually. Yet, <code>composer status</code> shows <code>No local changes</code>. Does this mean, that Composer itself does not check contents of each package's folder for local changes, only operates on differences between <code>composer.json</code> and <code>composer.lock</code>?</p>