[TASK] show version (if available) (#123)

circle.yml

@@ -7,7 +7,7 @@ jobs:
     steps:
       - checkout
       - run: go get -t -d -v ./...
-      - run: go install github.com/FreifunkBremen/yanic
+      - run: go install -ldflags "-X github.com/FreifunkBremen/yanic/cmd.VERSION=`git -C $GOPATH/src/github.com/FreifunkBremen/yanic rev-parse HEAD`" github.com/FreifunkBremen/yanic
       - store_artifacts:
           path: /go/bin/
           destination: yanic

cmd/version.go

@@ -0,0 +1,25 @@
+package cmd
+
+import (
+	"fmt"
+
+	"github.com/spf13/cobra"
+)
+
+var VERSION string
+
+// versionCMD to print version
+var versionCMD = &cobra.Command{
+	Use:   "version",
+	Short: "print version of yanic",
+	Run: func(cmd *cobra.Command, args []string) {
+
+		fmt.Printf("yanic version: %s\n", VERSION)
+	},
+}
+
+func init() {
+	if VERSION != "" {
+		RootCmd.AddCommand(versionCMD)
+	}
+}