ensure postfix version

.woodpecker.yml

@@ -10,6 +10,7 @@ pipeline:
       - latest
       build_args:
       - ALPINE_VERSION=${ALPINE_VERSION}
+      - POSTFIX_VERSION=${POSTFIX_VERSION}
       - BASE_IMAGE=registry.nulo.in/sutty/monit
     secrets:
     - docker_password
@@ -17,5 +18,6 @@ pipeline:
       branch: antifascista
       event: push
 matrix:
-  ALPINE_VERSION:
-  - 3.15.4
+  include:
+  - ALPINE_VERSION: 3.15.4
+    POSTFIX_VERSION: 3.6.6

Dockerfile

@@ -1,9 +1,10 @@
 ARG ALPINE_VERSION=3.13.6
 ARG BASE_IMAGE=sutty/monit
 FROM ${BASE_IMAGE}:${ALPINE_VERSION} AS build
+ARG POSTFIX_VERSION=3.6.6
 MAINTAINER "f <f@sutty.nl>"
 
-RUN apk add --no-cache postfix ca-certificates
+RUN apk add --no-cache postfix~${POSTFIX_VERSION} ca-certificates
 RUN install -dm 2750 -o root -g root /etc/ssl/private
 
 RUN apk add --no-cache gnutls-utils