Multistage builds in Docker 17.05

Dockerfile

FROM php as vendoring-image
RUN apt-get update && \
    apt-get install -y --no-install-recommends git zip
RUN curl --silent --show-error https://getcomposer.org/installer | php && \
    mv composer.phar /bin/composer
COPY ./composer.json ./composer.lock /app
WORKDIR /app
RUN composer install

# PS - This is the only image we want to push. Crazy, right?
FROM php:alpine as production-image
RUN mkdir /app
COPY --from=vendoring-image /app/vendors /app/vendors

Should be vendor not vendors