On MacOS, if a folder has custom icon, there would be an invisible file named Icon^M in it.
^M being carriage return. Kindly refer to https://superuser.com/questions/298785/icon-file-on-os-x-desktop for more details about such a file.
If I try to add the parent folder with M-x file-cache-add-directory, I get error
"Filecache: file /xxx/xxx/Icon does not exist"
Is it possible to let Emacs ignore this file?