Multi-repository docker-compose

I have two services, on two different GitLab repositories, deployed to the same host. I am currently using supervisord to run all of the services. The CI/CD for each repository pushes the code to the host.

I am trying to transition to using Docker, keeping the two repositories. I set up a Dockerfile for each service.
I have created a third repository with only a docker-compose.yml to build and run the two services.

I am looking for a way to have the docker-compose automatically update when I deploy one of the two repositories, instead of me having to manually do docker-compose pull every time.

My docker-compose:

version: "3.4"
services:
    redis:
        image: "redis:alpine"
    api:
        build: .
        command: gunicorn -c gunicorn_conf.py --bind 0.0.0.0:5000 --chdir server "app:app" --timeout 120
        volumes:
            - .:/app
        ports:
            - "8000:8000"
        depends_on:
            - redis
    celery-worker:
        build: .
        command: celery worker -A server.celery_config:celery
        volumes:
            - .:/app
        depends_on:
            - redis
    celery-beat:
        build: .
        command: celery beat -A server.celery_config:celery --loglevel=INFO
        volumes:
            - .:/app
        depends_on:
            - redis
    other-service:
        build: .
        command: python other-service.py
        volumes:
            - .:/other-service
        depends_on:
            - redis

Source: StackOverflow