make nebula a service that can install itself

cmd/nebula-service/main.go

@@ -0,0 +1,49 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"os"
+
+	"github.com/slackhq/nebula"
+)
+
+// A version string that can be set with
+//
+//     -ldflags "-X main.Build=SOMEVERSION"
+//
+// at compile-time.
+var Build string
+
+func main() {
+	serviceFlag := flag.String("service", "", "Control the system service.")
+	configPath := flag.String("config", "", "Path to either a file or directory to load configuration from")
+	configTest := flag.Bool("test", false, "Test the config and print the end result. Non zero exit indicates a faulty config")
+	printVersion := flag.Bool("version", false, "Print version")
+	printUsage := flag.Bool("help", false, "Print command line usage")
+
+	flag.Parse()
+
+	if *printVersion {
+		fmt.Printf("Build: %s\n", Build)
+		os.Exit(0)
+	}
+
+	if *printUsage {
+		flag.Usage()
+		os.Exit(0)
+	}
+
+	if *serviceFlag != "" {
+		doService(configPath, configTest, Build, serviceFlag)
+		os.Exit(1)
+	}
+
+	if *configPath == "" {
+		fmt.Println("-config flag must be set")
+		flag.Usage()
+		os.Exit(1)
+	}
+
+	nebula.Main(*configPath, *configTest, Build)
+}