Add version and commit hash to binary

Makefile

@@ -3,13 +3,16 @@
 .PHONY: test build
 .DEFAULT_GOAL := help
 
+GIT_COMMIT=$(shell git rev-list -1 HEAD)
+GIT_VERSION=$(shell git describe --abbrev=0 --tags)
+
 test: ## run tests
 	go test -v -cover -race `go list ./... | grep -v /vendor/`
 
 build: ## build binaries for distribution
-	GOOS=linux GOARCH=amd64 go build -o ddns-Linux-x86_64 .
-	GOOS=darwin GOARCH=amd64 go build -o ddns-Darwin-x86_64 .
-	GOOS=linux GOARCH=arm GOARM=7 go build -o ddns-Linux-armv7l .
+	GOOS=linux GOARCH=amd64 go build -ldflags "-X main.buildVersion=$(GIT_VERSION) -X main.buildCommitHash=$(GIT_COMMIT)" -o ddns-Linux-x86_64 .
+	GOOS=darwin GOARCH=amd64 go build -ldflags "-X main.buildVersion=$(GIT_VERSION) -X main.buildCommitHash=$(GIT_COMMIT)" -o ddns-Darwin-x86_64 .
+	GOOS=linux GOARCH=arm GOARM=7 go build -ldflags "-X main.buildVersion=$(GIT_VERSION) -X main.buildCommitHash=$(GIT_COMMIT)" -o ddns-Linux-armv7l .
 
 help:
 	@grep -E '^[a-zA-Z0-9_-]+:.*?## .*$$' $(MAKEFILE_LIST) | sort | awk 'BEGIN {FS = ":.*?## "}; {printf "\033[36m%-30s\033[0m %s\n", $$1, $$2}'

README.md

@@ -51,6 +51,7 @@ Usage of ./ddns:
       Location of the configuration file (default "$HOME/.ddns.yml")
   -req-timeout duration
       Request timeout to external resources (default 10s)
+  -v  Show version and exit
 ```
 
 **Configuration should be supplied.** By default it is read from `$HOME/.ddns.yml`.

main.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"flag"
+	"fmt"
 	"net/http"
 	"os"
 	"time"
@@ -17,6 +18,11 @@ import (
 	"github.com/skibish/ddns/notifier"
 )
 
+var (
+	buildVersion    string
+	buildCommitHash string
+)
+
 func main() {
 	log.SetFormatter(&log.TextFormatter{
 		DisableColors: true,
@@ -28,9 +34,15 @@ func main() {
 		reqTimeouts = flag.Duration("req-timeout", 10*time.Second, "Request timeout to external resources")
 		checkPeriod = flag.Duration("check-period", 5*time.Minute, "Check if IP has been changed period")
 		confFile    = flag.String("conf-file", "$HOME/.ddns.yml", "Location of the configuration file")
+		showVersion = flag.Bool("v", false, "Show version and exit")
 	)
 	flag.Parse()
 
+	if *showVersion {
+		fmt.Printf("Version: %s\nCommitHash: %s\n", buildVersion, buildCommitHash)
+		return
+	}
+
 	// read configuration
 	var errConf error
 	cf, errConf := conf.NewConfiguration(*confFile)