separate and optimize Dockerfile for master and develop

docker/Dockerfile

-FROM ubuntu:wily
-MAINTAINER caktux
-
-ENV DEBIAN_FRONTEND noninteractive
-
-# Usual update / upgrade
-RUN apt-get update
-RUN apt-get upgrade -q -y
-RUN apt-get dist-upgrade -q -y
-
-# Install Ethereum
-RUN apt-get install -q -y software-properties-common
-RUN add-apt-repository ppa:ethereum/ethereum
-RUN add-apt-repository ppa:ethereum/ethereum-dev
-RUN apt-get update
-RUN apt-get install -q -y geth
-
-EXPOSE 8545
-EXPOSE 30303
-
-ENTRYPOINT ["/usr/bin/geth"]

docker/develop/Dockerfile

+FROM ubuntu:wily
+MAINTAINER caktux
+
+ENV DEBIAN_FRONTEND noninteractive
+
+RUN apt-get update && \
+    apt-get upgrade -q -y && \
+    apt-get dist-upgrade -q -y && \
+    apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 923F6CA9 && \
+    echo "deb http://ppa.launchpad.net/ethereum/ethereum-dev/ubuntu wily main" | tee -a /etc/apt/sources.list.d/ethereum.list && \
+    apt-get update && \
+    apt-get install -q -y geth
+
+EXPOSE 8545
+EXPOSE 30303
+
+ENTRYPOINT ["/usr/bin/geth"]

docker/master/Dockerfile

+FROM ubuntu:wily
+MAINTAINER caktux
+
+ENV DEBIAN_FRONTEND noninteractive
+
+RUN apt-get update && \
+    apt-get upgrade -q -y && \
+    apt-get dist-upgrade -q -y && \
+    apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 923F6CA9 && \
+    echo "deb http://ppa.launchpad.net/ethereum/ethereum/ubuntu wily main" | tee -a /etc/apt/sources.list.d/ethereum.list && \
+    apt-get update && \
+    apt-get install -q -y geth
+
+EXPOSE 8545
+EXPOSE 30303
+
+ENTRYPOINT ["/usr/bin/geth"]