docker: introduce multi-stage image build (master, latest)

Relates to https://github.com/shaarli/Shaarli/issues/755
Relates to https://github.com/shaarli/Shaarli/pull/1072

See:
- https://docs.docker.com/develop/develop-images/multistage-build/
- https://hub.docker.com/r/library/composer/
- https://github.com/composer/docker
- https://github.com/docker-library/docs/tree/master/composer

Signed-off-by: VirtualTam <virtualtam@flibidi.net>

docker/alpine/Dockerfile.latest

@@ -1,9 +1,19 @@
+# Stage 1:
+# - Get Shaarli sources
+# - Resolve PHP dependencies with Composer
+FROM composer:latest as composer
+RUN curl -L https://github.com/shaarli/Shaarli/archive/latest.tar.gz | tar xzf - \
+    && mv Shaarli-latest shaarli \
+    && cd shaarli \
+    && composer --prefer-dist --no-dev install
+
+# Stage 2:
+# - Shaarli image
 FROM alpine:3.6
-MAINTAINER Shaarli Community
+LABEL maintainer="Shaarli Community"
 
 RUN apk --update --no-cache add \
         ca-certificates \
-        curl \
         nginx \
         php7 \
         php7-ctype \
@@ -15,7 +25,6 @@ RUN apk --update --no-cache add \
         php7-json \
         php7-mbstring \
         php7-openssl \
-        php7-phar \
         php7-session \
         php7-xml \
         php7-zlib \
@@ -25,22 +34,15 @@ COPY nginx.conf /etc/nginx/nginx.conf
 COPY php-fpm.conf /etc/php7/php-fpm.conf
 COPY services.d /etc/services.d
 
-RUN curl -sS https://getcomposer.org/installer | php7 -- --install-dir=/usr/local/bin --filename=composer \
-    && rm -rf /etc/php7/php-fpm.d/www.conf \
+RUN rm -rf /etc/php7/php-fpm.d/www.conf \
     && sed -i 's/post_max_size.*/post_max_size = 10M/' /etc/php7/php.ini \
     && sed -i 's/upload_max_filesize.*/upload_max_filesize = 10M/' /etc/php7/php.ini
 
 
 WORKDIR /var/www
-RUN curl -L https://github.com/shaarli/Shaarli/archive/latest.tar.gz | tar xzf - \
-    && mv Shaarli-latest shaarli \
-    && cd shaarli \
-    && composer --prefer-dist --no-dev install \
-    && rm -rf ~/.composer \
-    && chown -R nginx:nginx .
+COPY --from=composer /app/shaarli shaarli
 
 VOLUME /var/www/shaarli/data
-
 EXPOSE 80
 
 ENTRYPOINT ["/bin/s6-svscan", "/etc/services.d"]

docker/alpine/Dockerfile.master

@@ -1,9 +1,19 @@
+# Stage 1:
+# - Get Shaarli sources
+# - Resolve PHP dependencies with Composer
+FROM composer:latest as composer
+RUN curl -L https://github.com/shaarli/Shaarli/archive/master.tar.gz | tar xzf - \
+    && mv Shaarli-master shaarli \
+    && cd shaarli \
+    && composer --prefer-dist --no-dev install
+
+# Stage 2:
+# - Shaarli image
 FROM alpine:3.6
-MAINTAINER Shaarli Community
+LABEL maintainer="Shaarli Community"
 
 RUN apk --update --no-cache add \
         ca-certificates \
-        curl \
         nginx \
         php7 \
         php7-ctype \
@@ -15,7 +25,6 @@ RUN apk --update --no-cache add \
         php7-json \
         php7-mbstring \
         php7-openssl \
-        php7-phar \
         php7-session \
         php7-xml \
         php7-zlib \
@@ -25,20 +34,15 @@ COPY nginx.conf /etc/nginx/nginx.conf
 COPY php-fpm.conf /etc/php7/php-fpm.conf
 COPY services.d /etc/services.d
 
-RUN curl -sS https://getcomposer.org/installer | php7 -- --install-dir=/usr/local/bin --filename=composer \
-    && rm -rf /etc/php7/php-fpm.d/www.conf \
+RUN rm -rf /etc/php7/php-fpm.d/www.conf \
     && sed -i 's/post_max_size.*/post_max_size = 10M/' /etc/php7/php.ini \
     && sed -i 's/upload_max_filesize.*/upload_max_filesize = 10M/' /etc/php7/php.ini
 
 
 WORKDIR /var/www
-RUN curl -L https://github.com/shaarli/Shaarli/archive/master.tar.gz | tar xzf - \
-    && mv Shaarli-master shaarli \
-    && cd shaarli \
-    && composer --prefer-dist --no-dev install \
-    && rm -rf ~/.composer \
-    && chown -R nginx:nginx .
+COPY --from=composer /app/shaarli shaarli
 
+RUN chown -R nginx:nginx .
 VOLUME /var/www/shaarli/data
 
 EXPOSE 80