Set version dynamically

Also, add -version command

Makefile

@@ -1,6 +1,9 @@
+VERSION := $(shell git describe --exact-match --tags 2>/dev/null)
+LDFLAGS = -X main.version=$(VERSION)
+
 build:
 	go get -u github.com/shuLhan/go-bindata/...
 	$$GOPATH/bin/go-bindata -pkg dbanon -o src/bindata.go etc/*
 	GO111MODULE=on go get ./...
 	GO111MODULE=on go test $$GOPATH/src/github.com/mpchadwick/dbanon/src
-	GO111MODULE=on go build -o dbanon main.go
+	GO111MODULE=on go build -ldflags "$(LDFLAGS)" -o dbanon main.go

main.go

@@ -12,7 +12,7 @@ import (
 	"os"
 )
 
-const version = "0.2.2"
+var version string
 
 const slug = "mpchadwick/dbanon"
 
@@ -35,9 +35,15 @@ func selfUpdate() error {
 func main() {
 	requested := flag.String("config", "", "Configuration to use. magento2 is included out-of-box. Alternately, supply path to file")
 	update := flag.Bool("update", false, "Auto update dbanon to the newest version")
+	ver := flag.Bool("version", false, "Get current version")
 
 	flag.Parse()
 
+	if *ver {
+		fmt.Println(version)
+		os.Exit(0)
+	}
+
 	if *update {
 		if err := selfUpdate(); err != nil {
 			fmt.Fprintln(os.Stderr, err)