bug#13921: 24.2; Misbehavior of expand-file-name on Cygwin with Emacs 24.2

[Eli Zaretskii <eliz@gnu.org>]

> Date: Tue, 12 Mar 2013 20:45:45 -0400
> From: Barry OReilly <gundaetiapo@gmail.com>
> Cc: 13921@debbugs.gnu.org
> 
>    source-directory is a variable defined in `lread.c'.
>    Its value is "d:/devel/emacs/release/emacs24/emacs-24.2/"
> 
>    Documentation:
>    Directory in which Emacs sources were found when Emacs was built.
>    You cannot count on them to still be there!
> 
> I did not find this /devel/emacs/release/emacs24/emacs-24.2/ on my system,
> nor is it the kind of path I would create.

source-directory is where Emacs was built.  And since you didn't build
it yourself, this reflects the directory where whoever built it did
that.

And since Cygwin passes to Emacs a file name without a drive letter,
the logic in autoload.el causes the D: drive letter be added to
/home/epich/sw/cedet/lisp/cedet, because it doesn't expect a
semi-absolute file name like that, it expects either a relative file
name or a fully-qualified absolute one.

So this is a direct result of launching a native w32 Emacs from a
Cygwin Bash.