services:
  composer:
    environment:
      SSH_AUTH_SOCK: /run/host-services/ssh-auth.sock
    volumes:
      - .:/code
      # Share the ssh-agent's socket to be able to install dependencies from private repositories via Composer.
      # We are not actually pointing at the socket on a host system, we are pointing at some other special machinery
      # in Docker Desktop for macOS that enables specifically the SSH agent forwarding.
      # Requires Docker Desktop 2.2+ in case of macOS. Related issue: https://github.com/docker/for-mac/issues/410
      # The appropriate SSH key must be added to the SSH agent on the host before running composer install.
      - /run/host-services/ssh-auth.sock:/run/host-services/ssh-auth.sock