Add -version argument to show version.

+ log the version on startup.

Makefile

@@ -17,6 +17,8 @@
 IMAGE_NAME=quay.io/k8scsi/csi-attacher
 IMAGE_VERSION=canary
 
+REV=$(shell git describe --long --match='v*' --dirty)
+
 ifdef V
 TESTARGS = -v -args -alsologtostderr -v 5
 else
@@ -28,7 +30,7 @@ all: csi-attacher
 
 csi-attacher:
 	mkdir -p bin
-	CGO_ENABLED=0 GOOS=linux go build -a -ldflags '-extldflags "-static"' -o ./bin/csi-attacher ./cmd/csi-attacher
+	CGO_ENABLED=0 GOOS=linux go build -a -ldflags '-X main.version=$(REV) -extldflags "-static"' -o ./bin/csi-attacher ./cmd/csi-attacher
 
 clean:
 	-rm -rf bin

cmd/csi-attacher/main.go

@@ -52,12 +52,24 @@ var (
 	connectionTimeout = flag.Duration("connection-timeout", 1*time.Minute, "Timeout for waiting for CSI driver socket.")
 	csiAddress        = flag.String("csi-address", "/run/csi/socket", "Address of the CSI driver socket.")
 	dummy             = flag.Bool("dummy", false, "Run in dummy mode, i.e. not connecting to CSI driver and marking everything as attached. Expected CSI driver name is \"csi/dummy\".")
+	showVersion       = flag.Bool("version", false, "Show version.")
+)
+
+var (
+	version = "unknown"
 )
 
 func main() {
 	flag.Set("logtostderr", "true")
 	flag.Parse()
 
+	if *showVersion {
+		fmt.Println(os.Args[0], version)
+		return
+	}
+
+	glog.Infof("Version: %s", version)
+
 	// Create the client config. Use kubeconfig if given, otherwise assume in-cluster.
 	config, err := buildConfig(*kubeconfig)
 	if err != nil {