From the repository as is

• docker compose watch
• docker compose exec app bash
  • ls -al
    • empty directory /var/www/html

With COPY . /var/www/html in Dockerfile

• add COPY . /var/www/html
• docker compose build app
• docker compose watch
• change index.html to whatever
• changes are reflected in container and in the browser (http://localhost:8080/index.html)
• kill watch
• docker compose down
• docker compose watch
  • no changes made to index.html can be seen in container or in browser