add ldflags on build with main.commit and main.branch to Makefile

Makefile

@@ -1,6 +1,9 @@
 TEST=.
 BENCH=.
 COVERPROFILE=/tmp/c.out
+BRANCH=`git rev-parse --abbrev-ref HEAD`
+COMMIT=`git rev-parse --short HEAD`
+GOLDFLAGS="-X main.branch $(BRANCH) -X main.commit $(COMMIT)"
 
 bench: benchpreq
 	go test -v -test.bench=$(BENCH)
@@ -31,7 +34,7 @@ get:
 
 build: get
 	@mkdir -p bin
-	@go build -a -o bin/bolt-`git rev-parse --short HEAD` ./cmd/bolt
+	@go build -ldflags=$(GOLDFLAGS) -a -o bin/bolt-`git rev-parse --short HEAD` ./cmd/bolt
 
 test: fmt errcheck
 	@go get github.com/stretchr/testify/assert

cmd/bolt/main.go

@@ -9,6 +9,8 @@ import (
 	"github.com/codegangsta/cli"
 )
 
+var branch, commit string
+
 func main() {
 	log.SetFlags(0)
 	NewApp().Run(os.Args)
@@ -19,7 +21,7 @@ func NewApp() *cli.App {
 	app := cli.NewApp()
 	app.Name = "bolt"
 	app.Usage = "BoltDB toolkit"
-	app.Version = "0.1.0"
+	app.Version = fmt.Sprintf("0.1.0 (%s %s)", branch, commit)
 	app.Commands = []cli.Command{
 		{
 			Name:  "get",