Add Docker Hub hooks

Author: zhengyao-lin

hooks/post_checkout

@@ -0,0 +1,4 @@
+#!/bin/bash
+
+# recursively pull all submodules after checkout
+git submodule update --init --recursive --depth 1

hooks/post_push

@@ -0,0 +1,5 @@
+#!/bin/bash
+
+# push to another tag named after the commit it
+docker tag $IMAGE_NAME $DOCKER_REPO:$SOURCE_COMMIT
+docker push $DOCKER_REPO:$SOURCE_COMMIT