New build system

Far more idiomatic.

Dockerfile

@@ -0,0 +1,16 @@
+FROM alpine:3.5
+
+COPY docker/start.sh /bin/start.sh
+CMD ["/bin/start.sh"]
+
+COPY main.go /go/src/github.com/discourse/discourse-auth-proxy/
+
+RUN apk add --no-cache -t build-deps build-base git go mercurial \
+	&& export GOPATH=/go \
+	&& cd /go/src/github.com/discourse/discourse-auth-proxy \
+	&& go get \
+	&& go build -o /bin/discourse-auth-proxy \
+	&& apk del --purge build-deps \
+	# Don't ask me why, but purging the go package leaves behind about
+	# 8MB of cruft in /usr/lib/go which we have to nuke by hand
+	&& rm -rf /go /usr/lib/go

build

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+#!/bin/bash
+
+docker build --build-arg=http_proxy=$http_proxy -t discourse/auth-proxy .
+docker push discourse/auth-proxy