bug#13272: 24.3.50; `diff' output header line shows MS Windows root incorrectly

[Eli Zaretskii]

> Date: Tue, 25 Dec 2012 05:44:53 +0200
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: 13272@debbugs.gnu.org
> 
> > From: "Drew Adams" <drew.adams@oracle.com>
> > Date: Mon, 24 Dec 2012 14:07:05 -0800
> > 
> > I'm seeing this now in the very first line of my `M-x diff' output:
> >  
> > diff -c c\:/foo/simple.el c\:/foo/simple-patched-2012-12-24.el
> 
> That's your diff.exe at work, I'm quite sure: it tries to quote the
> colon, because it's a Cygwin Diff and lives in the Unix world.

There's another possibility: that this quoting is done by
shell-quote-argument.  What do you get if you evaluate the following
expression?

   (shell-quote-argument "c:/foo/simple.el")

If you get the colon quoted with a backslash, then my crystal ball
says that you customized shell-file-name to point to the Cygwin Bash,
in which case this is normal behavior, see shell-quote-argument.