🎨 Refactor building a docker image

* Add linode extra
* Drop manual apk update and cleanup
* Put Molecule extras into env var
* Retrieve a Docker tag as pbr does

.dockerignore

@@ -0,0 +1 @@
+.gitignore

Dockerfile

@@ -0,0 +1,65 @@
+# This is a multi-stage build which requires Docker 17.05 or higher
+FROM python:3.7-alpine as molecule-builder
+
+WORKDIR /usr/src/molecule
+
+ENV PACKAGES="\
+    gcc \
+    git \
+    libffi-dev \
+    make \
+    musl-dev \
+    openssl-dev \
+    "
+RUN apk add --update --no-cache ${PACKAGES}
+
+ENV MOLECULE_EXTRAS="azure,docker,docs,ec2,gce,linode,lxc,openstack,vagrant,windows"
+
+ADD . .
+RUN \
+    pip wheel \
+    -w dist \
+    ".[${MOLECULE_EXTRAS}]"
+
+# ✄---------------------------------------------------------------------
+# This is an actual target container:
+
+FROM python:3.7-alpine
+LABEL maintainer "Ansible <info@ansible.com>"
+
+ENV PACKAGES="\
+    docker \
+    ruby \
+    "
+ENV BUILD_DEPS="\
+    gcc \
+    libc-dev \
+    make \
+    ruby-dev \
+    ruby-rdoc \
+    "
+
+ENV PIP_INSTALL_ARGS="\
+    --only-binary :all: \
+    --no-index \
+    -f /usr/src/molecule/dist \
+    "
+
+ENV GEM_PACKAGES="\
+    rubocop \
+    "
+
+ENV MOLECULE_EXTRAS="azure,docker,docs,ec2,gce,linode,lxc,openstack,vagrant,windows"
+
+COPY --from=molecule-builder \
+    /usr/src/molecule/dist \
+    /usr/src/molecule/dist
+
+RUN \
+    apk add --update --no-cache ${BUILD_DEPS} ${PACKAGES} && \
+    pip install ${PIP_INSTALL_ARGS} "molecule[${MOLECULE_EXTRAS}]" && \
+    gem install ${GEM_PACKAGES} && \
+    apk del --no-cache ${BUILD_DEPS} && \
+    rm -rf /root/.cache
+
+ENV SHELL /bin/bash

tox.ini

@@ -189,3 +189,29 @@ usedevelop = False
 commands =
     python -m setup checkdocs check --metadata --restructuredtext --strict --verbose
     twine check .tox/dist/*
+
+[testenv:build-docker]
+# skip under Windows
+platform = ^darwin|^linux
+# `usedevelop = True` overrided `skip_install` instruction, it's unwanted
+usedevelop = False
+# don't install Molecule in this env
+skip_install = True
+# don't install any Python dist deps
+deps =
+  pbr
+#  setuptools_scm
+# reset pre-commands
+commands_pre =
+# build the docker container
+commands =
+    sh -c '\
+    TAG=$(python -c "from pbr.packaging import get_version; print(get_version(\".\"))") && \
+    #TAG=$(python -c "from setuptools_scm import get_version; print(get_version())") && \
+    echo Building version "$TAG"... && \
+    sudo docker build \
+        --pull --rm \
+        {posargs:-t ansible/molecule:$TAG} .\
+    '
+whitelist_externals =
+    sh