title: git: can't push changes after using filter-branch to remove file
body: <p>I have an app on heroku, and unfortunately our git repository had some files that shouldn't be in it committed from the beginning.</p>
  
  <p>But now other people are about to collaborate in the project and those files are always creating merge conflicts, so I need to remove that. I've used this command to successfully remove those files from all commit history:</p>
  
  <p><code>git filter-branch --index-filter 'git rm --cached --ignore-unmatch -r foldername' HEAD</code></p>
  
  <p>But I can't push those changes to the server, I'm forced to pull before, therefore losing my changes through filter-branch.</p>
  
  <p>How can I push those changes to the server so we won't have conflict issues anymore?</p>
  
  <p>Thanks in advance.</p>