title: Git: How can I modify server's commit?
body: <p>I have already push some commits on my git server on EC2 , not on github.</p>
  
  <p>How can I modify those commits on the git server?</p>
  
  <p>Operation like
  remove commit, like rebasing, 
  change commit message</p>
  
  <p>Is it possible?</p>
  
  <p>Thanks so much.</p>