Add -version to show version info

Makefile

@@ -5,10 +5,13 @@ help:
 
 PROJECT=zkcli
 VERSION=$(shell cat main.go |grep 'version = "[0-9]\+.[0-9]\+.[0-9]\+"' | awk -F '"' '{print $$2}')
+GIT_COMMIT=$(shell git rev-parse --short HEAD)
+BUILT_TIME=$(shell date -u '+%FT%T%z')
 
 GOVERSION=$(shell go version)
 GOOS=$(word 1,$(subst /, ,$(lastword $(GOVERSION))))
 GOARCH=$(word 2,$(subst /, ,$(lastword $(GOVERSION))))
+LDFLAGS="-X main.gitCommit=${GIT_COMMIT} -X main.built=${BUILT_TIME}"
 
 ARCNAME=$(PROJECT)-$(VERSION)-$(GOOS)-$(GOARCH)
 RELDIR=$(ARCNAME)
@@ -20,7 +23,7 @@ release:
 	rm -rf $(DISTDIR)/$(RELDIR)
 	mkdir -p $(DISTDIR)/$(RELDIR)
 	go clean
-	GOOS=$(GOOS) GOARCH=$(GOARCH) go build
+	GOOS=$(GOOS) GOARCH=$(GOARCH) go build -ldflags ${LDFLAGS}
 	cp $(PROJECT)$(SUFFIX_EXE) $(DISTDIR)/$(RELDIR)/
 	tar czf $(DISTDIR)/$(ARCNAME).tar.gz -C $(DISTDIR) $(RELDIR)
 	go clean
@@ -35,4 +38,5 @@ release-all:
 lint:
 	gofmt -s -w .
 	golint .
+	golint core
 	go vet

main.go

@@ -10,15 +10,25 @@ import (
 	"github.com/let-us-go/zkcli/core"
 )
 
+var gitCommit = "unknown"
+var built = "unknown"
+
 const version = "0.1.0"
 
 func main() {
 	servers := flag.String("s", "127.0.0.1:2181", "Servers")
 	username := flag.String("u", "", "Username")
 	password := flag.String("p", "", "Password")
+	showVersion := flag.Bool("version", false, "Show version info")
 	flag.Parse()
 	args := flag.Args()
 
+	if *showVersion {
+		fmt.Printf("Version:\t%s\nGit commit:\t%s\nBuilt: %s\n",
+			version, gitCommit, built)
+		os.Exit(0)
+	}
+
 	config := core.NewConfig(strings.Split(*servers, ","))
 	if *username != "" && *password != "" {
 		auth := core.NewAuth(