Do not patch Dockerfiles in CI

When building the Dockerfiles for development, those images are mainly used to
create a reproducible build-environment. The source code is bind-mounted into
the image at runtime; there is no need to create an image with the actual
source code, and copying the source code into the image would lead to a new
image being created for each code-change (possibly leading up to many "dangling"
images for previous code-changes).

However, when building (and using) the development images in CI, bind-mounting
is not an option, because the daemon is running remotely.

To make this work, the circle-ci script patched the Dockerfiles when CI is run;
adding a `COPY` to the respective Dockerfiles.

Patching Dockerfiles is not really a "best practice" and, even though the source
code does not and up in the image, the source would still be _sent_ to the daemon
for each build (unless BuildKit is used).

This patch updates the makefiles, circle-ci script, and Dockerfiles;

- When building the Dockerfiles locally, pipe the Dockerfile through stdin.
  Doing so, prevents the build-context from being sent to the daemon. This speeds
  up the build, and doesn't fill up the Docker "temp" directory with content that's
  not used
- Now that no content is sent, add the COPY instructions to the Dockerfiles, and
  remove the code in the circle-ci script to "live patch" the Dockerfiles.

Before this patch is applied (with cache):

```
$ time make -f docker.Makefile build_shell_validate_image
docker build -t docker-cli-shell-validate -f ./dockerfiles/Dockerfile.shellcheck .
Sending build context to Docker daemon     41MB
Step 1/2 : FROM    debian:stretch-slim
...
Successfully built 81e14e8ad856
Successfully tagged docker-cli-shell-validate:latest

2.75 real         0.45 user         0.56 sys
```

After this patch is applied (with cache)::

```
$ time make -f docker.Makefile build_shell_validate_image
cat ./dockerfiles/Dockerfile.shellcheck | docker build -t docker-cli-shell-validate -
Sending build context to Docker daemon  2.048kB
Step 1/2 : FROM    debian:stretch-slim
...
Successfully built 81e14e8ad856
Successfully tagged docker-cli-shell-validate:latest

0.33 real         0.07 user         0.08 sys
```

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

circle.yml

@@ -16,9 +16,7 @@ jobs:
       - run:
           name: "Lint"
           command: |
-            dockerfile=dockerfiles/Dockerfile.lint
+            docker build -f dockerfiles/Dockerfile.lint --tag cli-linter:$CIRCLE_BUILD_NUM .
-            echo "COPY . ." >> $dockerfile
-            docker build -f $dockerfile --tag cli-linter:$CIRCLE_BUILD_NUM .
             docker run --rm cli-linter:$CIRCLE_BUILD_NUM
 
   cross:
@@ -34,9 +32,7 @@ jobs:
       - run:
           name: "Cross"
           command: |
-            dockerfile=dockerfiles/Dockerfile.cross
+            docker build -f dockerfiles/Dockerfile.cross --tag cli-builder:$CIRCLE_BUILD_NUM .
-            echo "COPY . ." >> $dockerfile
-            docker build -f $dockerfile --tag cli-builder:$CIRCLE_BUILD_NUM .
             name=cross-$CIRCLE_BUILD_NUM-$CIRCLE_NODE_INDEX
             docker run \
                 -e CROSS_GROUP=$CIRCLE_NODE_INDEX \
@@ -60,9 +56,7 @@ jobs:
       - run:
           name: "Unit Test with Coverage"
           command: |
-            dockerfile=dockerfiles/Dockerfile.dev
+            docker build -f dockerfiles/Dockerfile.dev --tag cli-builder:$CIRCLE_BUILD_NUM .
-            echo "COPY . ." >> $dockerfile
-            docker build -f $dockerfile --tag cli-builder:$CIRCLE_BUILD_NUM .
             docker run --name \
                 test-$CIRCLE_BUILD_NUM cli-builder:$CIRCLE_BUILD_NUM \
                 make test-coverage
@@ -89,10 +83,8 @@ jobs:
       - run:
           name: "Validate Vendor, Docs, and Code Generation"
           command: |
-            dockerfile=dockerfiles/Dockerfile.dev
-            echo "COPY . ." >> $dockerfile
             rm -f .dockerignore # include .git
-            docker build -f $dockerfile --tag cli-builder-with-git:$CIRCLE_BUILD_NUM .
+            docker build -f dockerfiles/Dockerfile.dev --tag cli-builder-with-git:$CIRCLE_BUILD_NUM .
             docker run --rm cli-builder-with-git:$CIRCLE_BUILD_NUM \
                 make ci-validate
   shellcheck:
@@ -107,9 +99,7 @@ jobs:
       - run:
           name: "Run shellcheck"
           command: |
-            dockerfile=dockerfiles/Dockerfile.shellcheck
+            docker build -f dockerfiles/Dockerfile.shellcheck --tag cli-validator:$CIRCLE_BUILD_NUM .
-            echo "COPY . ." >> $dockerfile
-            docker build -f $dockerfile --tag cli-validator:$CIRCLE_BUILD_NUM .
             docker run --rm cli-validator:$CIRCLE_BUILD_NUM \
                 make shellcheck
 workflows:

docker.Makefile

@@ -17,24 +17,29 @@ ENVVARS = -e VERSION=$(VERSION) -e GITCOMMIT -e PLATFORM
 # build docker image (dockerfiles/Dockerfile.build)
 .PHONY: build_docker_image
 build_docker_image:
-	docker build ${DOCKER_BUILD_ARGS} -t $(DEV_DOCKER_IMAGE_NAME) -f ./dockerfiles/Dockerfile.dev .
+	# build dockerfile from stdin so that we don't send the build-context; source is bind-mounted in the development environment
+	cat ./dockerfiles/Dockerfile.dev | docker build ${DOCKER_BUILD_ARGS} -t $(DEV_DOCKER_IMAGE_NAME) -
 
 # build docker image having the linting tools (dockerfiles/Dockerfile.lint)
 .PHONY: build_linter_image
 build_linter_image:
-	docker build ${DOCKER_BUILD_ARGS} -t $(LINTER_IMAGE_NAME) -f ./dockerfiles/Dockerfile.lint .
+	# build dockerfile from stdin so that we don't send the build-context; source is bind-mounted in the development environment
+	cat ./dockerfiles/Dockerfile.lint | docker build ${DOCKER_BUILD_ARGS} -t $(LINTER_IMAGE_NAME) -
 
 .PHONY: build_cross_image
 build_cross_image:
-	docker build ${DOCKER_BUILD_ARGS} -t $(CROSS_IMAGE_NAME) -f ./dockerfiles/Dockerfile.cross .
+	# build dockerfile from stdin so that we don't send the build-context; source is bind-mounted in the development environment
+	cat ./dockerfiles/Dockerfile.cross | docker build ${DOCKER_BUILD_ARGS} -t $(CROSS_IMAGE_NAME) -
 
 .PHONY: build_shell_validate_image
 build_shell_validate_image:
-	docker build -t $(VALIDATE_IMAGE_NAME) -f ./dockerfiles/Dockerfile.shellcheck .
+	# build dockerfile from stdin so that we don't send the build-context; source is bind-mounted in the development environment
+	cat ./dockerfiles/Dockerfile.shellcheck | docker build -t $(VALIDATE_IMAGE_NAME) -
 
 .PHONY: build_binary_native_image
 build_binary_native_image:
-	docker build -t $(BINARY_NATIVE_IMAGE_NAME) -f ./dockerfiles/Dockerfile.binary-native .
+	# build dockerfile from stdin so that we don't send the build-context; source is bind-mounted in the development environment
+	cat ./dockerfiles/Dockerfile.binary-native | docker build -t $(BINARY_NATIVE_IMAGE_NAME) -
 
 .PHONY: build_e2e_image
 build_e2e_image:

dockerfiles/Dockerfile.cross

@@ -1,3 +1,4 @@
 FROM	dockercore/golang-cross:1.11.1@sha256:57ce59bec5445d27cc00f9e27fc171bea44eed7a9890df6eea6540f214300a01
 ENV     DISABLE_WARN_OUTSIDE_CONTAINER=1
 WORKDIR /go/src/github.com/docker/cli
+COPY    . .

dockerfiles/Dockerfile.dev

@@ -1,4 +1,3 @@
-
 FROM    golang:1.11.1-alpine
 
 RUN     apk add -U git make bash coreutils ca-certificates curl
@@ -22,3 +21,4 @@ ENV     CGO_ENABLED=0 \
         DISABLE_WARN_OUTSIDE_CONTAINER=1
 WORKDIR /go/src/github.com/docker/cli
 CMD     sh
+COPY    . .

dockerfiles/Dockerfile.lint

@@ -15,3 +15,4 @@ ENV     CGO_ENABLED=0
 ENV     DISABLE_WARN_OUTSIDE_CONTAINER=1
 ENTRYPOINT ["/usr/local/bin/gometalinter"]
 CMD     ["--config=gometalinter.json", "./..."]
+COPY    . .

dockerfiles/Dockerfile.shellcheck

@@ -7,3 +7,4 @@ RUN     apt-get update && \
 WORKDIR /go/src/github.com/docker/cli
 ENV     DISABLE_WARN_OUTSIDE_CONTAINER=1
 CMD     bash
+COPY    . .