git push heroku master error: src refspec master does not match any error: failed to push some refs to 'https://git.heroku.com/gadget-shop-api.git' code example

Example 1: git push heroku master error: src refspec master does not match any error: failed to push some refs to 'https://git.heroku.com/write-any.git'

git push heroku HEAD:master

Example 2: rror: src refspec master does not match any. error: failed to push some refs to 'https://git.heroku.com/thawing-retreat-68019.git'

git push heroku HEAD:master