Error in pushing rejected no cedar-supported app detected during Heroku deployment

Recently I learned rails (reference material http://railstutorial-china.org/rails3/). When Heroku is deployed (git push heroku master), the terminal prompts: push rejected no cedar-supported app detected error. After studying for a long time, the original version library path problem caused heroku to fail to judge the application type during deployment. My environment is myapp/first_app/(source code), and the version library is created under myapp. Therefore, an error is returned when I deploy it to heroku. Delete the existing version library, and re-create the database under first_app (source code root folder) and then deploy the database. No error message is displayed.