bug#28156: Emacs quietly munges symlink contents

[Eli Zaretskii]

> Cc: Eli Zaretskii <eliz@gnu.org>, Philipp Stephani <p.stephani2@gmail.com>,
>  28156@debbugs.gnu.org
> From: Paul Eggert <eggert@cs.ucla.edu>
> Date: Sun, 20 Aug 2017 11:53:55 -0700
> 
> (shell-command "ln -s '~' symlink")
> 0
> (file-symlink-p "symlink")
> "~"
> (rename-file "symlink" "/tmp/symlink")
> nil
> (file-symlink-p "/tmp/symlink")
> "/home/eggert"

If this is the problem, then let's solve it without affecting
make-symbolic-link.  The problem you show is in file-symlink-p and/or
in rename-file.  Let's solve it there, and let's solve it without
affecting the interactive callers of those functions.

> Here, rename-file quietly expands the symlink contents, which is a bug. As 
> far 
> as I can see, one cannot work around the bug by using Tramp quoting; for 
> example, (rename-file "/:symlink" "/:/tmp/symlink") does the same thing that 
> (rename-file "symlink" "/tmp/symlink") does.

But AFAIU, file-symlink-p can return a quoted name if its argument is
quoted.  Doesn't this allow to solve the problem?