add docker image build support

Dockerfile

@@ -0,0 +1,13 @@
+FROM golang:alpine as build
+ARG LD_FLAGS
+WORKDIR /go/src/github.com/ksonnet/ksonnet
+COPY . /go/src/github.com/ksonnet/ksonnet
+RUN CGO_ENABLED=0 GOOS=linux go build -o ks -ldflags="${LD_FLAGS}" ./cmd/ks
+
+FROM alpine:latest as certs
+RUN apk --update add ca-certificates
+
+FROM scratch
+COPY --from=certs /etc/ssl/certs/* /etc/ssl/certs/
+COPY --from=build /go/src/github.com/ksonnet/ksonnet/ks /bin/ks
+ENTRYPOINT ["/bin/ks"]

Makefile

@@ -16,12 +16,14 @@
 VERSION?=dev-$(shell date +%FT%T%z)
 KS_BIN?=ks
 
-APIMACHINERY_VER := $(shell dep status | grep k8s.io/apimachinery | awk '{print $$3}')
+APIMACHINERY_VER := $(shell grep -B1 k8s.io/apimachinery Gopkg.lock | head -n1 | cut -d'"' -f2)
 REVISION=$(shell git rev-parse HEAD)
+GIT_TAG=$(shell git describe --tags)
 
 GO = go
 EXTRA_GO_FLAGS =
-GO_FLAGS = -ldflags="-X main.version=$(VERSION) -X main.apimachineryVersion=$(APIMACHINERY_VER) -X generator.revision=$(REVISION) $(GO_LDFLAGS) " $(EXTRA_GO_FLAGS)
+LD_FLAGS = -X main.version=$(VERSION) -X main.apimachineryVersion=$(APIMACHINERY_VER) -X generator.revision=$(REVISION) $(GO_LDFLAGS)
+GO_FLAGS = -ldflags="$(LD_FLAGS) " $(EXTRA_GO_FLAGS)
 GOFMT = gofmt
 # GINKGO = "go test" also works if you want to avoid ginkgo tool
 GINKGO = ginkgo
@@ -39,12 +41,20 @@ INTEGRATION_TEST_FIXTURES = ./fixtures
 
 all: ks docs
 
-ks:
+Gopkg.lock: Gopkg.toml
+	dep ensure
+	touch Gopkg.lock
+	$(eval APIMACHINERY_VER := $(shell grep -B1 k8s.io/apimachinery Gopkg.lock | head -n1 | cut -d'"' -f2))
+
+ks: Gopkg.lock
 	$(GO) build -o $(KS_BIN) $(GO_FLAGS) ./cmd/ks
 
 docs:
 	$(DOC_GEN_FILE)
 
+docker-image: Gopkg.lock
+	docker build -t ks:$(GIT_TAG) --build-arg LD_FLAGS="$(LD_FLAGS)" .
+
 install:
 	$(GO) build -o $(GOPATH)/bin/ks $(GO_FLAGS) ./cmd/ks
 

README.md

@@ -33,6 +33,10 @@ brew install ksonnet/tap/ks
 
 See the [releases page](https://github.com/ksonnet/ksonnet/releases) to download the latest released binary.
 
+### Build a docker image
+
+A docker image can be built and used similarly to our manual build [as seen here](/docs/docker-image-build.md) 
+
 ### Manually build and install
 
 You can download and manually build from source by following [these instructions](/docs/build-install.md).

docs/docker-image-build.md

@@ -0,0 +1,30 @@
+# Build a `ks` docker image
+
+The intended use case for building a docker images is to run `ks` from CI/CD. As a development tool it is recommended to install `ks` locally, though it is still possible to use the docker image for development as well.
+
+Copy and paste the following commands:
+```bash
+# Clone the ksonnet repo into your GOPATH
+go get github.com/ksonnet/ksonnet
+
+# Build and install binary under shortname `ks` into $GOPATH/bin
+cd "${GOPATH}/src/github.com/ksonnet/ksonnet"
+make docker-image
+```
+
+# Running `ks` via docker
+
+In order to run via docker, the `ks` process needs access to a kubernetes config file, certificates, and the current working directory. We can set these up using mounts. Here's what it looks like running on a local cluster with minikube:
+
+```bash
+docker run -e KUBECONFIG="~/.kube/config" --mount type=bind,source="~/.kube/conifg",target="~/.kube/config" --mount type=bind,source="~/.minikube",target="~/.minikube" --mount type=bind,source="$(pwd)",target="$(pwd)" -w "$(pwd)" ks --help
+```
+
+This sets the $KUBECONFIG environment variable inside the container, mounts the config and the directory holding certificates (which can be found inside the kubeconfig), and mounts the current working directory so that the `ks` binary knows where to work.
+
+It is also possible to use aliases, though keep in mind that this sets the working directory statically to the directory of the app you are working on:
+
+```bash
+alias ks="docker run -e KUBECONFIG=/path/to/kube/config --mount type=bind,source=/path/to/kube/config,target=/path/to/kube/config --mount type=bind,source=/path/to/cert/dir,target=/path/to/cert/dir --mount type=bind,source=/path/to/app/dir,target=/path/to/app/dir -w /path/to/app/dir ks"
+ks env list
+```