Container for running composer comands like this:
docker run --rm -i -t vojtabiberle/composer-php5 /sbin/my_init --skip-startup-files --quiet -- /sbin/setuser webapp /usr/bin/composer
This is not so much helpful, but with maker it will make much more sense.
In this container is removed xdebug and php-fpm.
Is here changed to /composer so you can mount your ~/.composer folder to /composer inside container and share everything (include credentials).
Is here set to true, so you can run composer as root withouth warning.
All other variables are same as in php5 container.