version: '2'
volumes: 
  resin-data:
services:
  service1:
    volumes: 
      - 'resin-data:/data'
    build: ./service1
  service2:
    volumes: 
      - 'resin-data:/data'
    build:
      context: ./service2
      dockerfile: Dockerfile-alt
      args:
        - 'COMPOSE_ARG=an argument defined in the docker-compose.yml file'