Dockerfile.e2e: move frozen-images to a separate stage

Signed-off-by: Sebastiaan van Stijn <[email protected]>

Dockerfile.e2e

@@ -1,5 +1,4 @@
-## Step 1: Build tests
-FROM golang:1.12.4-alpine as builder
+FROM golang:1.12.4-alpine as base
 
 RUN apk --no-cache add \
     bash \
@@ -9,17 +8,22 @@ RUN apk --no-cache add \
     lvm2-dev \
     jq
 
+RUN mkdir -p /build/
 RUN mkdir -p /go/src/github.com/docker/docker/
 WORKDIR /go/src/github.com/docker/docker/
 
-# Generate frozen images
-COPY contrib/download-frozen-image-v2.sh contrib/download-frozen-image-v2.sh
-RUN contrib/download-frozen-image-v2.sh /output/docker-frozen-images \
+FROM base AS frozen-images
+# Get useful and necessary Hub images so we can "docker load" locally instead of pulling
+COPY contrib/download-frozen-image-v2.sh /
+RUN /download-frozen-image-v2.sh /build \
 	buildpack-deps:jessie@sha256:dd86dced7c9cd2a724e779730f0a53f93b7ef42228d4344b25ce9a42a1486251 \
 	busybox:latest@sha256:bbc3a03235220b170ba48a157dd097dd1379299370e1ed99ce976df0355d24f0 \
 	busybox:glibc@sha256:0b55a30394294ab23b9afd58fab94e61a923f5834fba7ddbae7f8e0c11ba85e6 \
 	debian:jessie@sha256:287a20c5f73087ab406e6b364833e3fb7b3ae63ca0eb3486555dc27ed32c6e60 \
 	hello-world:latest@sha256:be0cd392e45be79ffeffa6b05338b98ebb16c87b255f48e297ec7f98e123905c
+# See also ensureFrozenImagesLinux() in "integration-cli/fixtures_linux_daemon_test.go" (which needs to be updated when adding images to this list)
+
+FROM base AS builder
 
 # Install dockercli
 # Please edit hack/dockerfile/install/<name>.installer to update them.
@@ -38,7 +42,7 @@ RUN CGO_ENABLED=0 go build -buildmode=pie -o /output/httpserver github.com/docke
 RUN hack/make.sh build-integration-test-binary
 RUN mkdir -p /output/tests && find . -name test.main -exec cp --parents '{}' /output/tests \;
 
-## Step 2: Generate testing image
+## Generate testing image
 FROM alpine:3.9 as runner
 
 # GNU tar is used for generating the emptyfs image
@@ -64,7 +68,7 @@ COPY integration-cli/fixtures   /tests/integration-cli/fixtures
 COPY hack/test/e2e-run.sh /scripts/run.sh
 COPY hack/make/.ensure-emptyfs /scripts/ensure-emptyfs.sh
 
-COPY --from=builder /output/docker-frozen-images /docker-frozen-images
+COPY --from=frozen-images /build/ /docker-frozen-images
 COPY --from=builder /output/httpserver /tests/contrib/httpserver/httpserver
 COPY --from=builder /output/tests /tests
 COPY --from=builder /usr/local/bin/docker /usr/bin/docker