support pipes

gpgit.go

@@ -163,9 +163,12 @@ func main() {
 	if err != nil {
 		log.Fatal(err)
 	}
+
+	if fi.Mode()&os.ModeNamedPipe == 0 {
 		if fi.Size() == 0 {
 			log.Fatal("stdin is empty")
 		}
+	}
 
 	data, err := ioutil.ReadAll(os.Stdin)
 	rawEml := string(data)