cmd: add version subcommand to dexctl

closes #220

build

@@ -11,7 +11,7 @@ mkdir -p $GOPATH/src/github.com/coreos/
 
 LD_FLAGS="-X main.version=$(./git-version)"
 go build -o bin/dex-worker -ldflags="$LD_FLAGS" github.com/coreos/dex/cmd/dex-worker
-go build -o bin/dexctl github.com/coreos/dex/cmd/dexctl
+go build -o bin/dexctl -ldflags="$LD_FLAGS" github.com/coreos/dex/cmd/dexctl
 go build -o bin/dex-overlord -ldflags="$LD_FLAGS" github.com/coreos/dex/cmd/dex-overlord
 go build -o bin/example-app github.com/coreos/dex/examples/app
 go build -o bin/example-cli github.com/coreos/dex/examples/cli

cmd/dexctl/command_version.go

+package main
+
+import "github.com/spf13/cobra"
+
+var (
+	// set by the top level build script
+	version = ""
+
+	cmdVersion = &cobra.Command{
+		Use:   "version",
+		Short: "Print the dexctl version.",
+		Long:  "Print the dexctl version.",
+		Run: func(cmd *cobra.Command, args []string) {
+			stdout(version)
+		},
+	}
+)
+
+func init() {
+	rootCmd.AddCommand(cmdVersion)
+}