title: Docker Compose build context from git repository with Dockerfile inside folder
body: <p>I would like to build a new image in my docker compose project using a git repository as I need to change some ARG vars.</p>
  
  <p>My concern is that the Dockerfile is inside a folder of the git repository.</p>
  
  <p>How can be specified a folder as build context using a git repository?</p>
  
  <p>Repository: <a href="https://github.com/wodby/drupal-php/blob/master/7/Dockerfile" rel="noreferrer">https://github.com/wodby/drupal-php/blob/master/7/Dockerfile</a></p>
  
  <pre><code>version: "2"
  services:
    php:
      build:
        context: https://github.com/wodby/drupal-php.git
        dockerfile: 7/Dockerfile
        args:
           - BASE_IMAGE_TAG=7.1
           - WODBY_USER_ID=117
           - WODBY_GROUP_ID=111
        volumes:
            - ./:/var/www/html
  </code></pre>
  
  <p>I've tried the dockerfile property: "FOLDER/" + Dockerfile</p>
  
  <p>But the repository uses relative paths, and it doesn't find dependencies:</p>
  
  <pre><code> ---&gt; 6cc2006e9102
  Step 7/9 : COPY templates /etc/gotpl/
  ERROR: Service 'phpe' failed to build: COPY failed: stat /var/lib/docker/tmp/docker-builder740707850/templates: no such file or directory
  </code></pre>