bug#550: 23.0.60; A case where file-truename ignores case on w32

["Lennart Borgman (gmail)" <lennart.borgman@gmail.com>]

Jason Rumney wrote:
> Lennart Borgman (gmail) wrote:
>> I got a bug report from a user concerning nXhtml. The problem seems to
>> be that Emacs ignores case in an existing directory name.
> 
> Only when the file does not exist. In that case, w32-long-file-name
> returns nil and the original string that was passed in to file-truename
> is used. The solution is probably to recursively descend the directory
> heirarchy until we find a directory that exists, and call
> w32-long-file-name on that.

I suggest replacing

   (or (w32-long-file-name filename) filename)))

in `true-filename' with

   (let ((w32-filename (w32-long-file-name filename))
         (root filename)
         w32-root)
     (while (not w32-filename)
       (when (eq ?/ (car (last (append root nil))))
         (setq root (substring root 0 -1)))
       (setq root (file-name-directory root))
       (if (not root)
           (setq w32-filename filename)
         (setq w32-root (w32-long-file-name root))
         (when w32-root
           (setq w32-filename
                 (concat w32-root
                         (substring filename (length w32-root)))))))
     w32-filename)