An image to edit rails credentials

Dockerfile

# build:
#   $ docker build -t rails_cred .
#
# usage:
#   $ docker run -it --rm \
#       -e RAILS_MASTER_KEY=$RAILS_MASTER_KEY \
#       -v `pwd`/config/credentials.yml.enc:/app/config/credentials.yml.enc \
#       -v `pwd`/config/credentials:/app/config/credentials \
#       rails_cred

FROM ruby:2.7.1-alpine

WORKDIR /app

ENV RAILS_VERSION=6.0.3.2
ENV EDITOR=vim

RUN apk update && apk add --update \
     build-base \
     vim \
     && rm -rf /var/cache/apk/*

RUN gem i rails --no-document --version $RAILS_VERSION
RUN rails new \
      --skip-gemfile \
      --skip-git \
      --skip-keeps \
      --skip-action-mailer \
      --skip-action-mailbox \
      --skip-action-text \
      --skip-active-record \
      --skip-active-storage \
      --skip-puma \
      --skip-action-cable \
      --skip-sprockets \
      --skip-spring \
      --skip-listen \
      --skip-javascript \
      --skip-turbolinks \
      --skip-test \
      --skip-system-test \
      --skip-bootsnap \
      --skip-webpack-install \
      .
RUN bundle init \
      && echo "gem 'rails', '$RAILS_VERSION'" >> Gemfile \
      && bundle install

ENTRYPOINT ["bin/rails", "credentials:edit"]