test_compos/docker-compose.yml

services:
  git_cloner:
    image: alpine/git
    volumes:
      - /data/py:/repo
    command: >
      sh -c "
      if [ ! -d /repo/.git ]; then
        git clone https://git.xander.cx.ua/Xanders25/test_compos.git /repo &&
        echo 'Repository cloned';
      else
        echo 'Repository already exists';
      fi;
      "

  app:
    build:
      context: /data/py
    dockerfile: Dockerfile
    working_dir: /app
    command: python app.py
    ports:
      - "5000:5000"
    depends_on:
      - git_cloner