Add build script, generate version string on build time, modify usage and add version info

.gitignore

@@ -22,4 +22,4 @@ go.work
 go.work.sum
 
 # build
-ass
+ass_v*

args.go

@@ -5,6 +5,7 @@ package main
 
 import (
 	"flag"
+	"fmt"
 )
 
 var configFilepath string
@@ -12,6 +13,15 @@ var privateKeyFilepath string
 var logFlag bool
 
 func ParseCommandline() bool {
+	flag.Usage = func () {
+		fmt.Println(`Usage: ass -config <string> -pkey <string> [-log]
+
+  -config <string>   The path to the config file (required)
+  -pkey <string>     The path to the private key file (required)
+  -log               Enable logging of messages
+
+version:`, Version)
+	}
 	flag.StringVar(&configFilepath, "config", "", "The path to the config file (required)")
 	flag.StringVar(&privateKeyFilepath, "pkey", "", "The path to the private key file (required)")
 	flag.BoolVar(&logFlag, "log", false, "Enable logging of messages")

build.sh

@@ -0,0 +1,10 @@
+#!/usr/bin/env bash
+
+ver="$(git rev-parse --short HEAD)"
+
+if ! git diff-index --quiet HEAD
+then
+    ver="${ver}-dev"
+fi
+
+go build -ldflags="-X 'main.Version=${ver}'" -o ass_v${ver}

main.go

@@ -5,6 +5,8 @@ package main
 
 import "os"
 
+var Version = "dev"
+
 func main() {
 	if ParseCommandline() {
 		ParseConfig(configFilepath)