src refspec main does not match any heroku 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: heroku error: src refspec master does not match any.

git add .
git commit -m "Initial commit"
git push heroku HEAD:master