Verify that vendored files are correct

Signed-off-by: Daniel Nephin <dnephin@docker.com>

Makefile

@@ -25,3 +25,13 @@ cross: clean
 	@gox -output build/docker-{{.OS}}-{{.Arch}} \
 		 -osarch="linux/arm linux/amd64 darwin/amd64 windows/amd64" \
 		 github.com/docker/cli/cmd/docker
+
+vendor: vendor.conf
+	@vndr 2> /dev/null
+	@if [ "`git status --porcelain -- vendor 2>/dev/nul`" ]; then \
+		echo; echo "vendoring is wrong. These files were changed:"; \
+		echo; git status --porcelain -- vendor 2>/dev/nul; \
+		echo; exit 1; \
+	fi;
+
+ci: cross test

circle.yml

@@ -14,4 +14,10 @@ jobs:
             docker run cli-linter
       - run:
           name: "Build and Unit Test"
-          command: docker build -f dockerfiles/Dockerfile.ci .
+          command: |
+            docker build -f dockerfiles/Dockerfile.ci --tag cli-builder .
+            docker run cli-builder
+      - run:
+          name: "Vendor"
+          command: |
+            docker run cli-builder make vendor

dockerfiles/Dockerfile.ci

@@ -24,7 +24,4 @@ COPY    . /go/src/github.com/docker/cli
 ENV     CGO_ENABLED=0
 WORKDIR /go/src/github.com/docker/cli
 
-RUN     make cross
-RUN     make test
-
-CMD     sh
+CMD     ["make", "ci"]