Add -version

Makefile

@@ -1,11 +1,14 @@
 .SILENT :
 .PHONY : docker-gen clean fmt
 
+TAG:=`git describe --abbrev=0 --tags`
+LDFLAGS:=-X main.buildVersion $(TAG)
+
 all: docker-gen
 
 docker-gen:
 	echo "Building docker-gen"
-	go build
+	go build -ldflags "$(LDFLAGS)"
 
 dist-clean:
 	rm -rf dist
@@ -17,5 +20,5 @@ dist: dist-clean
 
 release: dist
 	godep restore
-	tar -cvzf docker-gen-linux-amd64-latest.tar.gz -C dist/linux/amd64 docker-gen
-	tar -cvzf docker-gen-linux-i386-latest.tar.gz -C dist/linux/i386 docker-gen
+	tar -cvzf docker-gen-linux-amd64-$(TAG).tar.gz -C dist/linux/amd64 docker-gen
+	tar -cvzf docker-gen-linux-i386-$(TAG).tar.gz -C dist/linux/i386 docker-gen

docker-gen.go

@@ -15,6 +15,8 @@ import (
 )
 
 var (
+	buildVersion  string
+	version       bool
 	watch         bool
 	notifyCmd     string
 	onlyExposed   bool
@@ -198,6 +200,7 @@ func generateFromEvents(client *docker.Client, configs ConfigFile) {
 }
 
 func initFlags() {
+	flag.BoolVar(&version, "version", false, "show version")
 	flag.BoolVar(&watch, "watch", false, "watch for container changes")
 	flag.BoolVar(&onlyExposed, "only-exposed", false, "only include containers with exposed ports")
 	flag.BoolVar(&onlyPublished, "only-published", false, "only include containers with published ports (implies -only-exposed)")
@@ -211,6 +214,11 @@ func initFlags() {
 func main() {
 	initFlags()
 
+	if version {
+		fmt.Println(buildVersion)
+		return
+	}
+
 	if flag.NArg() < 1 && configFile == "" {
 		usage()
 		os.Exit(1)