Fix Dockerfile

Properly use Docker caching

Author: pointlessone

Dockerfile

@@ -1,33 +1,35 @@
 FROM node:6.10.0-slim
 LABEL maintainer "Code Climate <hello@codeclimate.com>"
 
-RUN apt-key adv --fetch-keys http://dl.yarnpkg.com/debian/pubkey.gpg && \
-    echo "deb http://dl.yarnpkg.com/debian/ stable main" | tee /etc/apt/sources.list.d/yarn.list && \
-    apt-get update
+RUN adduser --uid 9000 --gecos "" --disabled-password app
 
 WORKDIR /usr/src/app
-COPY bin/docs ./bin/docs
-COPY engine.json package.json yarn.lock ./
 
-RUN mkdir /usr/local/node_modules
 ENV PREFIX=/usr/local/node_modules
 ENV PATH=$PREFIX/.bin:$PATH
 ENV NODE_PATH=$PREFIX
 ENV NPM_CONFIG_PREFIX=$PREFIX
 
-RUN apt-get install -y git jq yarn && \
+RUN mkdir $PREFIX
+
+COPY bin/docs ./bin/docs
+COPY engine.json package.json yarn.lock ./
+
+RUN apt-key adv --fetch-keys http://dl.yarnpkg.com/debian/pubkey.gpg && \
+    echo "deb http://dl.yarnpkg.com/debian/ stable main" | tee /etc/apt/sources.list.d/yarn.list && \
+    apt-get update && \
+    apt-get install -y git jq yarn && \
     yarn config set prefix $PREFIX && \
     yarn install --modules-folder $PREFIX && \
+    chown -R app:app $PREFIX && \
     version="v$(yarn list eslint | grep eslint | sed -n 's/.*@//p')" && \
     bin/docs "$version" && \
     cat engine.json | jq ".version = \"$version\"" > /engine.json && \
     apt-get purge -y git jq yarn && \
     apt-get autoremove --yes
 
-RUN adduser --uid 9000 --gecos "" --disabled-password app
 COPY . ./
 RUN chown -R app:app ./
-RUN chown -R app:app $PREFIX
 
 USER app