Docker Cloud build phase hooks

Must be located in the root of each docker build context
i.e., every stack folder

tensorflow-notebook/hooks/post_push

@@ -0,0 +1,13 @@
+#!/bin/bash
+
+# Tag the latest build with the short git sha. Push the tag in addition
+# to the "latest" tag already pushed.
+GIT_SHA_TAG=${SOURCE_COMMIT:0:12}
+docker tag $IMAGE_NAME $DOCKER_REPO:$GIT_SHA_TAG
+docker push $DOCKER_REPO:$GIT_SHA_TAG
+
+# Invoke all downstream build triggers.
+for url in $(echo $NEXT_BUILD_TRIGGERS | sed "s/,/ /g")
+do
+    curl -X POST $url
+done