Refactor cmdVersion to cli package

cmd/headscale/cli/version.go

@@ -0,0 +1,23 @@
+package cli
+
+import (
+	"fmt"
+	"github.com/spf13/cobra"
+	"strings"
+)
+
+var version = "dev"
+
+var VersionCmd = &cobra.Command{
+	Use:   "version",
+	Short: "Print the version.",
+	Long:  "The version of headscale.",
+	Run: func(cmd *cobra.Command, args []string) {
+		o, _ := cmd.Flags().GetString("output")
+		if strings.HasPrefix(o, "json") {
+			JsonOutput(map[string]string{"version": version}, nil, o)
+			return
+		}
+		fmt.Println(version)
+	},
+}