Docker多阶段构建复制上一阶段（取决于顺序）

Question

我有Dockerfile：

FROM php:7.2.10-fpm-alpine as build

RUN apk upgrade --update && apk --no-cache add \
    gcc g++ make git autoconf tzdata openntpd libcurl curl-dev coreutils \
    freetype-dev libxpm-dev libjpeg-turbo-dev libvpx-dev \
    libpng-dev ca-certificates libressl libressl-dev libxml2-dev postgresql-dev icu-dev rabbitmq-c-dev

RUN docker-php-ext-configure intl \
    && docker-php-ext-configure opcache \
    && docker-php-ext-configure gd --with-freetype-dir=/usr/include/ \
    --with-jpeg-dir=/usr/include/ --with-png-dir=/usr/include/ \
    --with-xpm-dir=/usr/include/

RUN docker-php-ext-install -j$(nproc) \
    gd \
    pdo_pgsql \
    xmlrpc \
    zip \
    bcmath \
    intl \
    opcache \
    pcntl

# Install dependencies
RUN docker-php-source extract \
    && pecl install redis-4.1.1 apcu-5.1.12 amqp-1.9.3
RUN docker-php-ext-enable redis apcu amqp \
    && docker-php-source delete

# Add timezone
RUN rm /etc/localtime && \
    ln -s /usr/share/zoneinfo/UTC /etc/localtime && \
    "date"

# Install composer
RUN curl -sS https://getcomposer.org/installer | \
    php -- --install-dir=/usr/local/bin --filename=composer

# Cleanup
RUN rm -rf /var/cache/apk/* \
    && find / -type f -iname \*.apk-new -delete \
    && rm -rf /var/cache/apk/*

ADD php.ini /usr/local/etc/php/php.ini
ADD opcache.ini  /usr/local/etc/php/conf.d/opcache.ini
ADD www.conf /usr/local/etc/php/php-fpm.d/www.conf
ADD php-fpm.conf /usr/local/etc/php/php-fpm.d/php-fpm

EXPOSE 9000

CMD ["php-fpm"]

#Dev
FROM build as dev

ADD xdebug.ini /usr/local/etc/php/conf.d/xdebug.ini
RUN docker-php-source extract && pecl install xdebug-2.6.1
RUN docker-php-ext-enable xdebug && docker-php-source delete

#Production
FROM build as prod

ARG REPOSITORY_URL
ARG CHECKOUT_POSITION

RUN mkdir /var/www/project
RUN git clone $REPOSITORY_URL /var/www/project \
    && cd /var/www/project \
    && git reset --hard $CHECKOUT_POSITION \
    && env APP_ENV=prod composer install --no-dev --optimize-autoloader \
    && chown -R www-data:www-data /var/www/project

WORKDIR /var/www/project

USER www-data

当我从开发阶段开始使用docker build --target prod依赖项进行生产时（xdebug等）。

如果prod阶段移至dev之上，则prod的dev阶段复制依赖项。

可能是什么？

Docker版本18.06.1-ce，内部版本e68fc7a

UPD：Dockerfile已更新

代码太多，无法保存。代码太多，无法保存。代码太多，无法保存。

谢谢。