anchor.diff:      libxml2-dev \
       libxslt-dev \
       mysql-client \
  -    postgresql \
  +    openssl-dev \
  +    readline-dev \
       redis \
       rsync \
       ruby \
  
positive.code:     tar \
      zlib-dev && \
    rm -rf /var/cache/apk/*
  
  # Install ruby gems.
  RUN \
  
negative.code: ENV \
    HOME=/home/backups \
    BACKUP_CONFIG_DIR=/etc/backups \
    BACKUP_DATA_DIR=/var/lib/backups \
    PG_VERSION=9.6.1
  
  # Install base packages.
  RUN \
  