title: composer update without a cascade update
body: <p>I own two projects</p>
  
  <p>-The project A</p>
  
  <p>-The project B</p>
  
  <hr>
  
  <p>Project A "require" project B (with @dev version)</p>
  
  <p>Project B "require <strong>lot of stuff</strong>"</p>
  
  <p>When I do a</p>
  
  <blockquote>
    <p>composer update myname/project_b</p>
  </blockquote>
  
  <p>composer also makes an update of "<strong>lot of stuff</strong>", which can be time consuming, and I have to update frequently without knowing if the package has changed.</p>
  
  <p>So I had the idea to make a script with the following algorithm: <code>
  Partial update (~=git pull) of *myname/project_b*; 
  If *vendor/myname/project_b* has changed {
      do a full composer update.
  }</code></p>
  
  <p>The problem is that I have no idea how to do the "partial update".
  A git pull on the vendor directory keep prompt for username and password.</p>
  
  <p>Another approach could be to retrieve the id of the last commit of the repository with the version taken by composer, but again, I have no idea how to do it.</p>