Improve cache behaviour

pleroma.dockerfile

@@ -1,25 +1,42 @@
 FROM elixir:1.6-alpine
 
-WORKDIR /pleroma
+env MIX_HOME /mix
+env MIX_ARCHIVES /mix-archives
 
 # Prepare system
 RUN apk add --no-cache --virtual .build alpine-sdk git rsync
 
 # Perform a clone that can be cached
-RUN git clone https://git.pleroma.social/pleroma/pleroma.git .
+WORKDIR /pleroma
+RUN git clone --progress https://git.pleroma.social/pleroma/pleroma.git .
 
-# Prepare pleroma
-ADD ./docker-config.exs /docker-config.exs
+# Bust the cache with a build arg
+# that is different on every build
+ARG __BUST_CACHE
+ENV __BUST_CACHE $__BUST_CACHE
+
+# Update pleroma
 ARG PLEROMA_VERSION
 RUN \
     git checkout $PLEROMA_VERSION && \
-    git pull --rebase --autostash && \
+    git pull --rebase --autostash
+
+# Inject config
+ADD ./docker-config.exs /docker-config.exs
+RUN \
     ln -s /docker-config.exs config/prod.secret.exs && \
     ln -s /docker-config.exs config/dev.secret.exs
 
+# Correct paths
+WORKDIR /
+VOLUME /custom.d
+
 # Register entrypoint
 ADD ./entrypoint.ash /
 RUN chmod +x /entrypoint.ash
 CMD ["/entrypoint.ash"]
 
+# Call entrypoint to precompile pleroma
+RUN /entrypoint.ash onbuild
+
 EXPOSE 4000