tests: Refactor Dockerfile to multi-stage (more caching during development)

The previous refactor traded build step caching for smaller image size,
which in turn made fast caching of built images possible, and allowed us
to speed up CI builds. But almost any change in Dockerfile required full
rebuild of everything (vim & taskwarrior), so changes to the Dockerfile
became more painful.

This commit refactors the Dockerfile to use multi-stage builds, which
brings build caching back: vim & taskwarrior are built in separate
stages, which are cached step by step, and then the build artifacts are
copied into the main tests image and runtime dependencies are installed.

There's a catch, of course: --cache-from doesn't work with multi-stage
images unless the experimental BuildKit backend and its inline cache
export are enabled. This requires docker 19.03, which shouldn't be hard
to obtain but isn't installed by default on Travis CI.

.github/workflows/tests.yaml

@@ -36,7 +36,8 @@ jobs:
           ) | sha256sum | read -r tag _
           docker login "$DOCKER_REGISTRY" -u "$GITHUB_USER" -p "$GITHUB_TOKEN" || :
           docker pull "$DOCKER_CACHE_IMAGE":"$tag" || :
-          docker build \
+          DOCKER_BUILDKIT=1 docker build \
+            --build-arg BUILDKIT_INLINE_CACHE=1 \
             --cache-from "$DOCKER_CACHE_IMAGE":"$tag" \
             ${ALPINE_VERSION:+--build-arg ALPINE_VERSION="$ALPINE_VERSION"} \
             ${PYTHON_VERSION:+--build-arg PYTHON_VERSION="$PYTHON_VERSION"} \

Dockerfile

@@ -1,105 +1,91 @@
 ARG ALPINE_VERSION=3.12
 ARG PYTHON_VERSION=3
-
-FROM python:${PYTHON_VERSION}-alpine${ALPINE_VERSION}
-
 ARG TASK_VERSION=v2.5.1
 ARG VIM_VERSION=v8.2.0716
 ARG VIMWIKI_VERSION=master
 
-RUN set -ex \
- && apk add --no-cache --virtual .taskwiki-test-deps \
-    git \
-    make \
-    tzdata \
-    xvfb-run \
- && ln -sf /usr/share/zoneinfo/Etc/UTC /etc/localtime \
- && true
 
-RUN set -ex \
+FROM python:${PYTHON_VERSION}-alpine${ALPINE_VERSION} AS build
- \
+
- && : install vim $VIM_VERSION \
+
- \
+FROM build AS build-vim
- && apk add --no-cache --virtual .vim-build-deps \
+RUN apk add --no-cache \
     gcc \
     git \
     gtk+3.0-dev \
     libxt-dev \
     make \
     musl-dev \
-    ncurses-dev \
+    ncurses-dev
-    patchelf \
+ARG VIM_VERSION
- && cd /usr/src \
+RUN git clone --depth 1 --recurse-submodules --shallow-submodules \
- && git clone --depth 1 --recurse-submodules --shallow-submodules --branch $VIM_VERSION \
+    --branch $VIM_VERSION https://github.com/vim/vim /usr/src/vim
-    https://github.com/vim/vim \
+WORKDIR /usr/src/vim
- && cd vim \
+# "backport" https://github.com/vim/vim/commit/16d7eced1a08565a9837db8067c7b9db5ed68854
- && sed -i -e '/#\s*undef _POSIX_THREADS/d' src/if_python3.c \
+RUN sed -i -e '/#\s*undef _POSIX_THREADS/d' src/if_python3.c
- && ./configure --prefix=/opt/vim --enable-pythoninterp --enable-python3interp --enable-gui=gtk3 \
+RUN ./configure --prefix=/opt/vim --enable-pythoninterp --enable-python3interp --enable-gui=gtk3
- && make -j$(nproc) \
+RUN make -j$(nproc)
- && make install \
+RUN make install
- && rm -rf /usr/src/vim \
+
- && patchelf --print-needed /opt/vim/bin/* \
+
-  | grep -v '^libpython' \
+FROM build AS build-taskwarrior
-  | sort -u \
+RUN apk add --no-cache \
-  | sed -e 's/^/so:/' \
-  | xargs -rt apk add --no-cache --virtual .vim-runtime-deps \
- \
- && : install taskwarrior $TASK_VERSION \
- \
- && apk add --no-cache --virtual .taskwarrior-build-deps \
     cmake \
     g++ \
     gcc \
     git \
     make \
-    patchelf \
+    util-linux-dev
-    util-linux-dev \
+ARG TASK_VERSION
- && cd /usr/src \
+RUN git clone --depth 1 --recurse-submodules --shallow-submodules \
- && git clone --depth 1 --recurse-submodules --shallow-submodules --branch $TASK_VERSION \
+    --branch $TASK_VERSION https://github.com/GothenburgBitFactory/taskwarrior /usr/src/taskwarrior
-    https://github.com/GothenburgBitFactory/taskwarrior \
+WORKDIR /usr/src/taskwarrior
- && cd taskwarrior \
+RUN cmake -DCMAKE_INSTALL_PREFIX=/opt/taskwarrior -DCMAKE_BUILD_TYPE=release -DENABLE_SYNC=OFF .
- && cmake -DCMAKE_INSTALL_PREFIX=/opt/taskwarrior -DCMAKE_BUILD_TYPE=release -DENABLE_SYNC=OFF . \
+RUN make -j$(nproc)
- && make -j$(nproc) \
+RUN make install
- && make install \
+
- && rm -rf /usr/src/taskwarrior \
+
- && patchelf --print-needed /opt/taskwarrior/bin/* \
+FROM build AS build-pip
-  | sort -u \
+# coverage needs to build a C extensions, otherwise it's slow
-  | sed -e 's/^/so:/' \
+RUN apk add --no-cache \
-  | xargs -rt apk add --no-cache --virtual .taskwarrior-runtime-deps \
- \
- && : install vimwiki $VIMWIKI_VERSION \
- \
- && mkdir -p /root/.vim/bundle \
- && cd /root/.vim/bundle \
- && git clone --depth 1 --recurse-submodules --shallow-submodules --branch $VIMWIKI_VERSION \
-    https://github.com/vimwiki/vimwiki \
- \
- && : install python test dependencies \
- \
- && apk add --no-cache --virtual .python-coverage-build-deps \
     gcc \
-    musl-dev \
+    musl-dev
- && pip install \
+RUN pip install --root=/opt/pip-root \
     coverage \
     coveralls \
     pytest \
     pytest-cov \
     pytest-xdist \
-    https://github.com/liskin/vimrunner-python/archive/8c19ff88050c09236e7519425bfae33c687483df.zip \
+    https://github.com/liskin/vimrunner-python/archive/8c19ff88050c09236e7519425bfae33c687483df.zip
- \
+COPY requirements.txt /tmp/taskwiki/requirements.txt
- && : clean up build dependencies \
+RUN pip install --root=/opt/pip-root \
- \
+    -r /tmp/taskwiki/requirements.txt
- && apk del --no-network .taskwarrior-build-deps \
- && apk del --no-network .vim-build-deps \
- && apk del --no-network .python-coverage-build-deps \
- && true
 
+
+FROM build AS tests
+RUN apk add --no-cache \
+    git \
+    make \
+    patchelf \
+    tzdata \
+    xvfb-run
+RUN ln -sf /usr/share/zoneinfo/Etc/UTC /etc/localtime
+
+COPY --from=build-vim /opt/vim/ /opt/vim/
+COPY --from=build-taskwarrior /opt/taskwarrior/ /opt/taskwarrior/
+COPY --from=build-pip /opt/pip-root/ /
+
+# install runtime deps of vim/taskwarrior
+RUN patchelf --print-needed /opt/*/bin/* \
+  | grep -v '^libpython' \
+  | sort -u \
+  | sed -e 's/^/so:/' \
+  | xargs -rt apk add --no-cache
 ENV PATH=/opt/vim/bin:/opt/taskwarrior/bin:$PATH
-RUN set -ex \
+RUN task --version && vim --version
- && task --version \
+
- && vim --version \
+ARG VIMWIKI_VERSION
- && true
+RUN git clone --depth 1 --recurse-submodules --shallow-submodules \
+    --branch $VIMWIKI_VERSION https://github.com/vimwiki/vimwiki /root/.vim/bundle/vimwiki
 
-COPY requirements.txt /root/.vim/bundle/taskwiki/
-RUN pip install -r /root/.vim/bundle/taskwiki/requirements.txt
 WORKDIR /root/.vim/bundle/taskwiki