title: How to make composer to use an exact SHA1 value?
body: <p>I want to make sure composer is using an exact version of a git repository by specifing the SHA1 of the commit. How can I do this?</p>
  
  <p>I tried just putting the sha1 code into the version string, but this does not work:</p>
  
  <pre><code> [UnexpectedValueException]                                                   
   Could not parse version constraint a93cbe224a6922f181f55c7a35bde0cf61a6a5a4  
  </code></pre>