avoid overwriting file or directory

fix https://github.com/chrislusf/seaweedfs/issues/777

weed/filer2/filer.go

@@ -132,6 +132,12 @@ func (f *Filer) CreateEntry(entry *Entry) error {
 			return fmt.Errorf("insert entry %s: %v", entry.FullPath, err)
 		}
 	} else {
+		if oldEntry.IsDirectory() && !entry.IsDirectory() {
+			return fmt.Errorf("existing %s is a directory", entry.FullPath)
+		}
+		if !oldEntry.IsDirectory() && entry.IsDirectory() {
+			return fmt.Errorf("existing %s is a file", entry.FullPath)
+		}
 		if err := f.store.UpdateEntry(entry); err != nil {
 			return fmt.Errorf("update entry %s: %v", entry.FullPath, err)
 		}