Read and process the desktop file in directory DIRNAME.
Look for a desktop file in DIRNAME, or if DIRNAME is omitted, look in
directories listed in `desktop-path'. If a desktop file is found, it
is processed and `desktop-after-read-hook' is run. If no desktop file
is found, clear the desktop and run `desktop-no-desktop-file-hook'.
This function is a no-op when Emacs is running in batch mode.
It returns t if a desktop file was loaded, nil otherwise. (fn &optional DIRNAME)