Add hooks to tag builds properly

Dockerfile

@@ -5,6 +5,11 @@ RUN cd /go/src/github.com/teran/relay && CGO_ENABLED=0 go build -o bin/relay .
 
 FROM alpine
 
+ARG VCS_REF
+
+LABEL org.label-schema.vcs-ref=$VCS_REF \
+      org.label-schema.vcs-url="https://github.com/teran/relay"
+
 RUN apk add --update --no-cache \
   ca-certificates && \
   rm -vf /var/cache/apk/*

hooks/build

@@ -0,0 +1,10 @@
+#!/bin/bash
+
+echo "Build hook running"
+
+VSC_REF=$(git rev-parse --short HEAD)
+
+docker build --build-arg BUILD_DATE=`date -u +"%Y-%m-%dT%H:%M:%SZ"` \
+             --build-arg VCS_REF=${VSC_REF} \
+             -t "${DOCKER_REPO}:latest" \
+             -t "${DOCKER_REPO}:git${VSC_REF}" .

hooks/post_push

@@ -0,0 +1,5 @@
+#!/bin/bash
+
+echo "Post push hook running"
+
+docker push $DOCKER_REPO