Re: abbreviate-file-name on Windows seems incorrect

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

Drew Adams wrote:
> On MS Windows, my $HOME is "c:\\". That is what is returned by (getenv
> "HOME"), and that is what I see in Windows itself, in the list of
> environment vars.
> 
> The code for `abbreviate-file-name' defines `abbreviated-home-dir' as
> follows, in order to be able to "substitute `~' for the user's home
> directory", as the doc string says:
> 
> (or abbreviated-home-dir
>     (setq abbreviated-home-dir
>           (let ((abbreviated-home-dir "$foo"))
>             (concat "^" (abbreviate-file-name
>                          (expand-file-name "~"))
>                     "\\(/\\|\\'\\)"))))
> 
> The comment for this code is as follows, which indicates that a slash is
> added to distinguish the home dir from a file in that dir:
> 
>     ;; We include a slash at the end, to avoid spurious matches
>     ;; such as `/usr/foobar' when the home dir is `/usr/foo'.
> 
> However, that is improper for a Windows home directory such as mine (not an
> uncommon value).  (expand-file-name "~") returns "c:/", which is correct,
> but the result for `abbreviated-home-dir' becomes "^c:/\\(/\\|\\'\\)", which
> is incorrect and useless, AFAICT. It should be something like
> "^c:\\(/\\|\\'\\)", I would think.
> 
> I would expect (abbreviate-file-name "c:/foo/bar") to return "~/foo/bar",
> but it returns "c:/foo/bar". If `abbreviated-home-dir' were
> "^c:\\(/\\|\\'\\)", then the result would be correct: "~/foo/bar".



If leave abbreviated-home-dir as "^c:/\\(/\\|\\'\\)" and you instead 
just comment out this part in abbreviate-file-name, does it works as you 
expect then? :

	       ;; MS-DOS root directories can come with a drive letter;
	       ;; Novell Netware allows drive letters beyond `Z:'.
	       (not (and (or (eq system-type 'ms-dos)
			     (eq system-type 'cygwin)
			     (eq system-type 'windows-nt))
			 (save-match-data
			   (string-match "^[a-zA-`]:/$" filename)))))