Add composer to the image

REPOSITORY                                      TAG                        IMAGE ID            CREATED              SIZE
elecena/python-php                              3.8-7.3-alpine-composer    f4227196bd92        About a minute ago   141MB
elecena/python-php                              3.8-7.3-alpine             c9cc8676df95        19 hours ago         139MB

Resolves #4

Dockerfile

@@ -1,9 +1,15 @@
 # elecena.pl (c) 2015-2020
 
+# @see https://hub.docker.com/_/composer
+FROM composer:1.10.5 AS php-composer
+
 # @see https://hub.docker.com/_/python/
 FROM python:3.8-alpine
 RUN pip install virtualenv && rm -rf /root/.cache
 
+# copy composer from the first stage
+COPY --from=php-composer /usr/bin/composer /usr/bin
+
 # install dependencies
 RUN apk update && apk add \
 	php7 \
@@ -38,12 +44,12 @@ RUN apk update && apk add \
 	php7-xmlwriter \
 	php7-xml \
 	php7-xsl \
-	&& rm -rf /tmp /var/log/* /var/cache/*
+	&& rm -rf /tmp/* /var/log/* /var/cache/*
 
 ENV PHP_VERSION 7.3.16
 
 # add an info script
 WORKDIR /opt
 
-RUN echo "echo -e '### Python'; python -V; virtualenv --version; echo -e '\n### PHP'; php -v; php -m" > info.sh
+RUN echo "echo -e '### Python'; python -V; virtualenv --version; echo -e '\n### PHP'; php -v; composer -V; php -m" > info.sh
 RUN chmod 744 info.sh

README.md

@@ -11,7 +11,7 @@ docker pull elecena/python-php
 
 ```
 REPOSITORY                                      TAG                        IMAGE ID            CREATED             SIZE
-elecena/python-php                              3.8-7.3-alpine             c9cc8676df95        36 minutes ago      139MB
+elecena/python-php                              3.8-7.3-alpine-composer    c9cc8676df95        6 minutes ago       141MB
 ```
 
 ## Installed software
@@ -28,6 +28,7 @@ PHP 7.3.16 (cli) (built: Mar 20 2020 11:26:40) ( NTS )
 Copyright (c) 1997-2018 The PHP Group
 Zend Engine v3.3.16, Copyright (c) 1998-2018 Zend Technologies
     with Zend OPcache v7.3.16, Copyright (c) 1999-2018, by Zend Technologies
+Composer version 1.10.5 2020-04-10 11:44:22
 [PHP Modules]
 calendar
 Core