Heroku PHP with bitbucket-pipelines.yml - git command not found

I spent hours and only found this thread, but the solution didn't help me.

My setup

• Laravel PHP info app with phpinfo view, no extras
• Bitbucket Cloud with Heroku pipeline
• Heroku app accordingly configured

The problem is, when I push changes to Bitbucket and these are then pushed to Heroku, the git command is not found.

Please see my bitbucket-pipelines.yml in link to pastebin.

When the pipeline step "Deploy to Heroku" runs, it aborts saying

+ git push 
https://heroku:$HEROKU_API_KEY@git.heroku.com/$HEROKU_APP_NAME.git HEAD

bash: git: command not found

In the build setup, the installation of git successfully finishes. See screenshot.

Why does the git command afterwards fail?

Thanks in advance!

via Chebli Mohamed