[CGKIELE-166] Add docs, decrease image size

Author: Christos KK Loverdos

docker/Dockerfile

@@ -8,11 +8,20 @@ ENV SBT_VERIFY_TAG ${SBT_VERIFY_TAG:-v0.4.1}
 ARG MANTIS_TAG
 ENV MANTIS_TAG ${MANTIS_TAG:-phase/iele_testnet}
 
+# The command `sbt dist` generates a zip file in the `target/universal` directory.
+# The value of `MANTIS_DIST_ZIP_NAME` must be the name of the generated zip,
+# excluding the extension.
+# So, for example, currently (commit `35e06611`) the `sbt dist` command
+# produces `target/universal/mantis-1.0-daedalus-rc1.zip`, so we can set
+# `MANTIS_DIST_ZIP_NAME` to be `mantis-1.0-daedalus-rc1`.
+# A glob like `mantis-*` also works and is more convenient, since it is invariant
+# with respect to the other part, which dependens on the software version.
 ARG MANTIS_DIST_ZIP_NAME
-ENV MANTIS_DIST_ZIP_NAME ${MANTIS_DIST_ZIP_NAME:-mantis-*.zip}
+ENV MANTIS_DIST_ZIP_NAME ${MANTIS_DIST_ZIP_NAME:-mantis-*}
 
 # Just install enough to get nix up and running
 RUN apt-get update \
+    && apt-get dist-upgrade -y \
     && apt-get install -y curl bzip2 locales \
     && locale-gen en_US.UTF-8 \
     && update-locale LC_ALL=en_US.UTF-8 LANG=en_US.UTF-8 \
@@ -22,15 +31,17 @@ RUN apt-get update \
     && su mantis -c 'curl https://nixos.org/nix/install | sh && . ~/.nix-profile/etc/profile.d/nix.sh && nix-channel --update && tail -n 1 ~/.profile >> ~/.bashrc' \
     && ln -s /home/mantis/mantis-dist/app /app \
     && apt-get purge -y curl bzip2 \
-    && apt-get clean autoremove
+    && apt-get clean -y \
+    && rm -rf /var/cache/debconf/* /var/lib/apt/lists/* /var/log/* /tmp/* /var/tmp/*
 
 USER mantis
 WORKDIR /home/mantis
 ENV USER mantis
 
 # install java, sbt, git, unzip
 RUN . ~/.nix-profile/etc/profile.d/nix.sh \
-    && nix-env -i openjdk-8u172b02 sbt-1.1.4 git unzip
+    && nix-env -i openjdk-8u172b02 sbt-1.1.4 git unzip \
+    && nix-collect-garbage
 
 # TODO: Could just use a nix-shell and garbage collect (e.g. git, unzip, sbt) after the installations ...
 RUN . ~/.nix-profile/etc/profile.d/nix.sh \
@@ -44,7 +55,7 @@ RUN . ~/.nix-profile/etc/profile.d/nix.sh \
     && git submodule update --init \
     && sbt 'set test in Test := {}' dist \
     && mkdir -p ~/mantis-dist/app \
-    && unzip -d ~/mantis-dist/app target/universal/$MANTIS_DIST_ZIP_NAME \
+    && unzip -d ~/mantis-dist/app target/universal/${MANTIS_DIST_ZIP_NAME}.zip \
     && mv ~/mantis-dist/app/*/* ~/mantis-dist/app \
     && rmdir ~/mantis-dist/app/$MANTIS_DIST_ZIP_NAME \
     && cd ~ \