heroku cli app rename code example
Example 1: heroku rename
heroku apps:remane --app <old-project-name> <new-project-name>
Example 2: renaming heroku app
$ git remote rm heroku
$ heroku git:remote -a newname
heroku apps:remane --app <old-project-name> <new-project-name>
$ git remote rm heroku
$ heroku git:remote -a newname