cleanup and use build args

.drone.yml

@@ -1,15 +1,12 @@
 pipeline:
 
-  build:
-    image: alpine:edge
-    commands:
-      - sed -i 's@<VERSION>@${VERSION}@' Dockerfile
-
   docker:
     image: plugins/docker
     repo: bunix42/jekyll
+    build_args:
+      - JEKYLL_VERSION=3.8.6
     tags:
-     - ${VERSION}
+      - ${JEKYLL_VERSION}
     secrets: [ docker_username, docker_password ]
 
   slack:
@@ -19,7 +16,7 @@ pipeline:
     secrets: [ slack_webhook ]
 
 matrix:
-  VERSION:
+  JEKYLL_VERSION:
     - 3.7.2
     - 3.8.6
     - 3.9.1

Dockerfile

@@ -1,14 +1,14 @@
 FROM alpine:3.14
 
-MAINTAINER Hanjo Meinhardt <hanjo@bunix.de>
+LABEL org.opencontainers.image.authors="hanjo@bunix.de"
 
 ENV dev_packages="ca-certificates build-base libffi-dev ruby-dev ruby-rdoc ruby-irb gcc make musl-dev"
 
-RUN apk update && apk upgrade \
-    && apk add ruby ruby-json libffi libstdc++ ${dev_packages} \
+RUN apk add --no-cache ruby ruby-json libffi libstdc++ ${dev_packages} \
     && rm -rf /var/cache/apk/*
 
-RUN gem install jekyll -v <VERSION> \
+ARG JEKYLL_VERSION
+RUN gem install jekyll -v ${JEKYLL_VERSION} \
     && gem install jekyll-paginate \
     && gem install jekyll-auto-image \
     && gem install jekyll-tidy \