bug#10489: 24.0.92; dired-do-copy may create infinite directory hierarchy

[Eli Zaretskii]

> From: "Drew Adams" <drew.adams@oracle.com>
> Date: Fri, 13 Jan 2012 06:14:01 -0800
> Cc: 10489@debbugs.gnu.org
> 
> FWIW, this is what Bookmark+ uses, based on some input from Michael:
> 
> (defun bmkp-same-file-p (file1 file2)
>   "Return non-nil if FILE1 and FILE2 name the same file.
> If either name is not absolute, then it is expanded relative to
> `default-directory' for the test."
>   (and (equal (file-remote-p file1) (file-remote-p file2))
>        (string= (file-truename (expand-file-name file1))
>                 (file-truename (expand-file-name file2)))))

Which is obviously wrong on case-insensitive filesystems.