title: Pushing a different set of files to different repositories
body: <p>I have a web app on Heroku that contains a configuration file with database login information.</p>
  
  <p>I want to push this project to Github as well, but without the configuration file.</p>
  
  <p>Making a new commit without that file would remove it from the HEAD, but it'd still be there in the previous commits, I don't want this file on Github in the first place.</p>
  
  <p>How can I do this?</p>