detect a filer path is a file or a directory

fix https://github.com/chrislusf/seaweedfs/issues/1004

weed/server/filer_server_handlers_read.go

@@ -21,7 +21,8 @@ import (
 func (fs *FilerServer) GetOrHeadHandler(w http.ResponseWriter, r *http.Request, isGetMethod bool) {
 
 	path := r.URL.Path
-	if strings.HasSuffix(path, "/") && len(path) > 1 {
+	isForDirectory := strings.HasSuffix(path, "/")
+	if isForDirectory && len(path) > 1 {
 		path = path[:len(path)-1]
 	}
 
@@ -47,6 +48,11 @@ func (fs *FilerServer) GetOrHeadHandler(w http.ResponseWriter, r *http.Request,
 		return
 	}
 
+	if isForDirectory {
+		w.WriteHeader(http.StatusNotFound)
+		return
+	}
+
 	if len(entry.Chunks) == 0 {
 		glog.V(1).Infof("no file chunks for %s, attr=%+v", path, entry.Attr)
 		stats.FilerRequestCounter.WithLabelValues("read.nocontent").Inc()