update

Signed-off-by: Jess Frazelle <acidburn@microsoft.com>

buildfromtarball/Dockerfile

@@ -0,0 +1,11 @@
+FROM docker
+
+RUN apk install --no-cache \
+	bash \
+	ca-certificates \
+	curl \
+	tar
+
+COPY build.sh /usr/local/bin/build
+
+ENTRYPOINT ["build"]

buildfromtarball/build.sh

@@ -0,0 +1,22 @@
+#!/bin/bash
+set -e
+set -o pipefail
+set -x
+
+tarball=$1
+image=$2
+
+volume=/build
+
+mkdir -p "$build"
+
+curl --fail --silent --show-error --location "$tarball" | tar xvz --strip=1 -C %s 2>/dev/null) || (echo ""; printf "ERROR: %%s\n" "Could not prepare an image." "Please verify that $tarball is still available and is publicly accessible."; exit 1)
+
+# Try to pull the image.
+docker pull "$image" || true
+
+cd "$build"
+
+docker build --cache-from "$image" -t "$image" .
+
+docker push "$image"