Add version command that prints compiled version

Fix #128

Makefile

@@ -3,8 +3,12 @@ all: gocode
 DOCKER_REGISTRY=gcr.io/must-override/
 S3_BUCKET=s3://must-override/
 
+ifndef VERSION
+  VERSION := git-$(shell git rev-parse --short HEAD)
+endif
+
 gocode:
-	GO15VENDOREXPERIMENT=1 go install k8s.io/kops/cmd/...
+	GO15VENDOREXPERIMENT=1 go install -ldflags "-X main.BuildVersion=${VERSION}" k8s.io/kops/cmd/...
 	ln -sfn ${GOPATH}/src/k8s.io/kops/upup/models/ ${GOPATH}/bin/models
 
 codegen:

cmd/kops/version.go

@@ -0,0 +1,42 @@
+package main
+
+import (
+	"github.com/spf13/cobra"
+	"github.com/golang/glog"
+	"fmt"
+)
+
+var (
+	// value overwritten during build. This can be used to resolve issues.
+	BuildVersion = "0.1"
+)
+
+type VersionCmd struct {
+	cobraCommand *cobra.Command
+}
+
+var versionCmd = VersionCmd{
+	cobraCommand: &cobra.Command{
+		Use:   "version",
+		Short: "Print the client version information",
+	},
+}
+
+func init() {
+	cmd := versionCmd.cobraCommand
+	rootCommand.cobraCommand.AddCommand(cmd)
+
+	cmd.Run = func(cmd *cobra.Command, args []string) {
+		err := versionCmd.Run()
+		if err != nil {
+			glog.Exitf("%v", err)
+		}
+	}
+}
+
+func (c *VersionCmd) Run() error {
+	fmt.Printf("Version %s\n", BuildVersion)
+
+	return nil
+}
+