Add project's Makefile, improve the Dockerfile.

Add targets to build operator and create docker images.
  Add scm-source.json to the Dockerfile.

Dockerfile

@@ -1,5 +1,8 @@
 FROM alpine
-ADD postgres-operator /usr/local/bin
+MAINTAINER Team ACID @ Zalando <team-acid@zalando.de>
 
-CMD ["/usr/local/bin/postgres-operator"] 
+ADD build/linux/postgres-operator /postgres-operator
+ADD scm-source.json /
+
+ENTRYPOINT ["/postres-operator"]
 

Makefile

@@ -0,0 +1,41 @@
+.PHONY: clean local linux macos docker push scm-source.json
+
+BINARY ?= postgres-operator
+BUILD_FLAGS ?= -i
+DOCKERFILE = Dockerfile
+IMAGE ?= pierone.example.com/acid/$(BINARY)
+TAG ?= $(VERSION)
+GITHEAD = $(shell git rev-parse --short HEAD)
+GITURL = $(shell git config --get remote.origin.url)
+GITSTATUS = $(shell git status --porcelain || echo "no changes")
+SOURCES = cmd/main.go
+VERSION ?= $(shell git describe --tags --always --dirty)
+IMAGE ?= pierone.example.com/acid/$(BINARY)
+
+default: local
+
+clean:
+	rm -rf build
+
+local: build/${BINARY}
+linux: build/linux/${BINARY}
+macos: build/macos/${BINARY}
+
+build/${BINARY}: ${SOURCES}
+	go build -o $@ $(BUILD_FLAGS) $^
+
+build/linux/${BINARY}: ${SOURCES}
+	GOOS=linux GOARCH=amd64 go build -o $@ ${BUILD_FLAGS} $^
+
+build/macos/${BINARY}: ${SOURCES}
+	GOOS=darwin GOARCH=amd64 go build -o $@ ${BUILD_FLAGS} $^
+
+docker: ${DOCKERFILE} scm-source.json linux
+	docker build --rm -t "$(IMAGE):$(TAG)" -f $< .
+
+push:
+	docker push "$(IMAGE):$(TAG)"
+
+scm-source.json: .git
+	echo '{\n "url": "$(GITURL)",\n "revision": "$(GITHEAD)",\n "author": "$(USER)",\n "status": "$(GITSTATUS)"\n}' > scm-source.json
+