title: Update file and commit with gitlab
body: <p>I want to change the context of file and commit by using gitlab api. I looked the api documentation and couldn't find a way to do it. 
  The documentation link is here;
  <a href="https://docs.gitlab.com/ee/api/" rel="nofollow noreferrer">https://docs.gitlab.com/ee/api/</a></p>
  
  <p>Is it possible to do change the file and commit it?  Do you have any example?</p>