postfix: use my pkg instead of internet one

pkg/postfix/Dockerfile

@@ -1,10 +1,15 @@
-FROM alpine:3.7
+FROM alpine
 MAINTAINER Pierre-Olivier Mercier <nemunaire@nemunai.re>
 
-RUN apk add --no-cache postfix
+RUN apk add --no-cache bash postfix
 
 EXPOSE 25
 
-CMD ["/usr/sbin/postfix", "-d"]
+ENV POSTFIX_maillog_file=/dev/stdout
+
+COPY docker-entrypoint.sh /docker-entrypoint.sh
+
+ENTRYPOINT ["/docker-entrypoint.sh"]
+CMD ["/usr/sbin/postfix", "start-fg"]
 
 LABEL org.mobyproject.config='{"binds": ["/etc/resolv.conf:/etc/resolv.conf"], "capabilities": ["CAP_NET_BIND_SERVICE"]}'

pkg/postfix/docker-entrypoint.sh

@@ -1,13 +1,7 @@
-#!/bin/sh
+#!/bin/bash
 
-set -e
-
-if [ `which unbound-$1 2>/dev/null` ]; then
-  set -- unbound-"$@"
-elif [ ! `which $1 2>/dev/null` ]; then
-  set -- unbound -dv "$@"
-fi
-
-unbound-anchor
+# POSTFIX_var env -> postconf -e var=$POSTFIX_var
+for e in ${!POSTFIX_*} ; do postconf -e "${e:8}=${!e}" ; done
+chown -R postfix:postfix /var/lib/postfix /var/mail /var/spool/postfix
 
 exec "$@"