FROM alpine:3.13

MAINTAINER Hanjo Meinhardt <hanjo@bunix.de>

ENV dev_packages="ca-certificates build-base libffi-dev ruby-dev ruby-rdoc ruby-irb"

RUN apk update && apk upgrade \
    && apk add ruby ruby-json ${dev_packages} \
    && rm -rf /var/cache/apk/*

RUN gem install jekyll -v <VERSION> \
    && gem install jekyll-paginate \
    && gem install jekyll-auto-image \
    && gem install jekyll-tidy \
    && gem install jekyll-sitemap

RUN apk del ${dev_packages}