renaming heroku app via terminal code example

Example 1: rename heroku app local

First update the name for the heroku app on the heroku dashboard (on the heroku website)
Then do this on terminal (Make sure you're in the right repository)

$ git remote rm heroku (Remove the remote from git)
$ heroku git:remote -a <new app name> (Add it back with it's new name)

Example 2: renaming heroku app

$ git remote rm heroku
$ heroku git:remote -a newname