title: Docker compose not prepending project name to the container names when running multiple instances
body: <p>I have a set of docker that I run using <code>docker-compose up -d</code> pretty basic so far</p>
  
  <p>I want to run multiple instances of my project and I have read this  <a href="https://stackoverflow.com/questions/43957259/run-multiple-docker-compose">Run multiple docker compose</a></p>
  
  <p>Now when running <code>docker-compose up -p PRNAME -d</code> compose is not prepending project name to containers like <code>prname_container1</code> and I'm getting the following error :</p>
  
  <pre><code>ERROR: for container1  Cannot create container for service service1: Conflict. The container name "/container1" is already in use by container "f7aeb2ef782556ae5b0". You have to remove (or rename) that container to be able to reuse that name.
  </code></pre>
  
  <p>I might be missing something out here.</p>
  
  <p>A part of my docker-compose.yml looks like </p>
  
  <pre><code>services:
    service1:
      image: "${PROJECT_REPO}:image"
      container_name: "container1"
      ports:
        - 443:443
        - 8000:80
      networks:
        - db
        - proxy
        - oauth
      depends_on:
        - db
  </code></pre>