bug#24057: 25.1.50; ffap interprets comments beginning with "//" as file path

[Eli Zaretskii]

> From: Noam Postavsky <npostavs@users.sourceforge.net>
> Date: Sat, 23 Jul 2016 14:02:36 -0400
> Cc: Kaushal Modi <kaushal.modi@gmail.com>, 24057@debbugs.gnu.org
> 
> On Sat, Jul 23, 2016 at 9:59 AM, Eli Zaretskii <eliz@gnu.org> wrote:
> >>  Did you try this on some system where "//tmp" is a valid file name,
> >>  which is different from "/tmp"?
> > You need to be on a system that supports that.  Windows is one of
> > them; not sure if there are any others left nowadays.
> 
> How does it work?
> 
> C:\Users\npostavs>echo foo > //tmp
> The specified path is invalid.
> 
> In Emacs:
> 
> Saving file //tmp...
> Directory `//' does not exist; create? (y or n) y
> basic-save-buffer-2: //: no such directory
> 
> This is on a newly-upgraded-to-Windows-10 box, Emacs 24.5

It's a UNC notation.  Normally used for network shares.  If you want
to use this locally, you will need to create a share first.  Valid UNC
file/directory names look like //machine/share.