bug#27871: 26.0.50; Bad handling of unmounted directory

[Eli Zaretskii]

> From: Philipp Stephani <p.stephani2@gmail.com>
> Date: Sat, 23 Sep 2017 11:33:13 +0000
> Cc: 27871@debbugs.gnu.org
> 
>  > What if there's a directory called literally "(unreachable)SOMETHING"?
> 
>  An absolute file name cannot start with "(unreachable)".
> 
> Yes, and getcwd and friends only return absolute filenames, and we only use 
> $PWD if it's absolute, so
> anything except '/' or a drive letter can't be a prefix in the success case. 
> I'll add a comment to that effect. 

Then why not just check that the first character is something other
than '/'?