feat(serverHandler/upload): allow upload file without dir prefix

Previously, if upload mode is "dirfile", uploaded file path must starts
with a directory prefix, e.g. "dir/to/file".

To allow upload files mixed with directories, remove this restriction.

Author: marjune163

src/serverHandler/upload.go

@@ -73,10 +73,9 @@ func (h *handler) saveUploadFiles(fsPrefix string, createDir, overwriteExists bo
 		fsInfix := ""
 		formname := part.FormName()
 		if formname == dirFile {
-			if slashIndex <= 0 {
-				continue
+			if slashIndex > 0 {
+				fsInfix = partFilename[0:slashIndex]
 			}
-			fsInfix = partFilename[0:slashIndex]
 		} else if formname == innerDirFile { // get file path, strip first level of dir
 			if slashIndex <= 0 {
 				continue