Build docker image using multi-stage builds and Alpine

Dockerfile

@@ -1,11 +1,11 @@
-FROM node:12.18.0
+FROM node:12.18.0 as builder
 LABEL maintainer="Automattic"
 
-WORKDIR    /calypso
+WORKDIR /calypso
 
 
-ENV        CONTAINER 'docker'
-ENV        PROGRESS=true
+ENV CONTAINER 'docker'
+ENV PROGRESS=true
 
 # Build a "base" layer
 #
@@ -17,26 +17,45 @@ ENV        PROGRESS=true
 # env-config.sh
 #   used by systems to overwrite some defaults
 #   such as the apt and npm mirrors
-COPY       ./env-config.sh /tmp/env-config.sh
-RUN        bash /tmp/env-config.sh
+COPY ./env-config.sh /tmp/env-config.sh
+RUN bash /tmp/env-config.sh
 
 # Build a "source" layer
 #
 # This layer is populated with up-to-date files from
 # Calypso development.
 COPY . /calypso/
-RUN yarn install --frozen-lockfile && yarn cache clean
+RUN yarn install --frozen-lockfile
 
 
 # Build the final layer
 #
 # This contains built environments of Calypso. It will
 # change any time any of the Calypso source-code changes.
-ARG        commit_sha="(unknown)"
-ENV        COMMIT_SHA $commit_sha
-
-ARG        workers
-RUN        WORKERS=$workers CALYPSO_ENV=production BUILD_TRANSLATION_CHUNKS=true yarn run build && rm -fr .cache
-
-USER       nobody
-CMD        NODE_ENV=production node build/bundle.js
+ARG commit_sha="(unknown)"
+ENV COMMIT_SHA $commit_sha
+
+ARG workers
+RUN WORKERS=$workers CALYPSO_ENV=production BUILD_TRANSLATION_CHUNKS=true yarn run build
+
+
+FROM node:12.18.0-alpine as app
+
+ARG commit_sha="(unknown)"
+ENV COMMIT_SHA=$commit_sha
+ENV NODE_ENV=production
+WORKDIR /calypso
+RUN apk add --no-cache tini
+COPY --from=builder --chown=nobody:nobody /calypso/node_modules /calypso/node_modules/
+COPY --from=builder --chown=nobody:nobody /calypso/packages /calypso/packages/
+COPY --from=builder --chown=nobody:nobody /calypso/config /calypso/config/
+COPY --from=builder --chown=nobody:nobody /calypso/client/node_modules /calypso/client/node_modules/
+COPY --from=builder --chown=nobody:nobody /calypso/client/server/devdocs/search-index.js /calypso/client/server/devdocs/
+COPY --from=builder --chown=nobody:nobody /calypso/client/server/bundler/*.json /calypso/client/server/bundler/
+COPY --from=builder --chown=nobody:nobody /calypso/client/webpack.config.js /calypso/client/
+COPY --from=builder --chown=nobody:nobody /calypso/build /calypso/build/
+COPY --from=builder --chown=nobody:nobody /calypso/public /calypso/public/
+
+USER nobody
+ENTRYPOINT ["/sbin/tini", "--"]
+CMD ["node", "build/bundle.js"]