title: How to remove unused dependencies from composer?
body: <p>I installed a package with composer, and it installed many other packages as dependencies.</p>
  
  <p>Now I uninstalled the main package with <code>composer remove packageauthor/packagename</code>, but all the old dependencies were not removed. I expected composer to clean up and only keep packages that are required according to <code>composer.json</code> and their dependencies.</p>
  
  <p>How can I force composer to clean up and remove all unused packages ?</p>