Docker best practices

- Install and remove OS and Go build deps in a single layer
- Use COPY instead of ADD
- WORKDIR now resolves ENV variables, use one
- Use VOLUMES for configuration and datastore
- Added launcher script start-inbucket.sh
- Made docker-run.sh more powerful

Dockerfile

@@ -4,19 +4,22 @@
 FROM golang:1.6-alpine
 MAINTAINER James Hillyerd, @jameshillyerd
 
-# Dependencies
-RUN apk update && apk add git
-
 # Configuration (WORKDIR doesn't support env vars)
 ENV INBUCKET_SRC $GOPATH/src/github.com/jhillyerd/inbucket
 ENV INBUCKET_HOME /opt/inbucket
-WORKDIR /opt/inbucket
-ENTRYPOINT ["bin/inbucket"]
-CMD ["/etc/opt/inbucket.conf"]
+WORKDIR $INBUCKET_HOME
+ENTRYPOINT ["/con/context/start-inbucket.sh"]
+CMD ["/con/configuration/inbucket.conf"]
 
 # Ports: SMTP, HTTP, POP3
 EXPOSE 10025 10080 10110
 
+# Persistent Volumes, following convention at:
+#   https://github.com/docker/docker/issues/9277
+# NOTE /con/context is also used, not exposed by default
+VOLUME /con/configuration
+VOLUME /con/data
+
 # Build Inbucket
-ADD . $INBUCKET_SRC/
+COPY . $INBUCKET_SRC/
 RUN "$INBUCKET_SRC/etc/docker/install.sh"