Add versioning for v1.0.0 (#11)

Jenkinsfile

@@ -9,8 +9,9 @@ pipeline {
         stage('Prepare') {
             steps {
                 checkout scm
+                sh 'git fetch --depth=500'
                 sh 'go get github.com/mitchellh/gox'
-                sh 'go get -u -v .'
+                sh 'go get -d -u -v ./cmd/protoplex'
                 sh 'mkdir -p builds'
             }
         }
@@ -19,7 +20,15 @@ pipeline {
                 CGO_ENABLED = '0'
             }
             steps {
-                sh 'gox -parallel=2 -ldflags="-s -w" -output="builds/{{.Dir}}_{{.OS}}_{{.Arch}}" ./cmd/protoplex'
+                sh '''
+                    version="$(git describe --tags --abbrev=0 HEAD || true)"
+                    if [ -z "${version}" ]; then
+                        version="v0.0.0"
+                    fi
+                    build="$(git rev-parse --short HEAD)"
+                    fullver="${version}+${build}"
+                    gox -parallel=2 -ldflags="-s -w -X main.version=${fullver}" -output="builds/{{.Dir}}_{{.OS}}_{{.Arch}}" ./cmd/protoplex
+                '''
             }
         }
         stage('Cleanup') {

cmd/protoplex/protoplex.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"fmt"
 	"os"
 
 	"github.com/Pandentia/protoplex/protoplex"
@@ -9,10 +10,24 @@ import (
 	"gopkg.in/alecthomas/kingpin.v2"
 )
 
+var version string
+
+func printVersion() {
+	if version == "" {
+		fmt.Println("Version has not been set.")
+		os.Exit(1)
+		return
+	}
+	fmt.Println(version)
+	os.Exit(0)
+}
+
 func main() {
 	app := kingpin.New("protoplex", "A fast and simple protocol multiplexer.")
 	logger := zerolog.New(os.Stdout).With().Timestamp().Logger()
 
+	version := app.Flag("version", "Prints the current program version").Short('V').Bool()
+
 	bind := app.Flag("bind", "The address to bind to").Short('b').Default("0.0.0.0:8443").String()
 	verbose := app.Flag("verbose", "Enables debug logging").Short('v').Bool()
 	pretty := app.Flag("pretty", "Enables pretty logging").Short('p').Bool()
@@ -27,6 +42,10 @@ func main() {
 
 	app.Parse(os.Args[1:])
 
+	if *version {
+		printVersion()
+	}
+
 	if *pretty {
 		logger = logger.Output(zerolog.ConsoleWriter{Out: os.Stderr})
 	}