bug#65598: Lock-file link target uses obsolete system-name variable

[Eli Zaretskii]

> From: JD Smith <jdtsmith@gmail.com>
> Date: Tue, 29 Aug 2023 13:55:45 -0400
> 
> The variable system-name is obsoleted in favor of the (system-name) function. 
>  But the lock file symlink target generated when file locks are enabled still 
> uses the value of the variable, not the function.
> 
> This is important when you need to override the name of the system.  In my 
> situation this is because (system-name) is dynamically updated as my laptop 
> is attached to different networks (host.local, host.some.fqdn, etc.), leading 
> to spurious "~/tmp/file locked by …” prompts as I move around.
> 
> I can easily fix this like:
> 
> (setq system-name  ; to prevent spurious locks as (system-name) changes
>       (replace-regexp-in-string (rx ?. (* any) eos) "" (system-name)))
> 
> but that utilizes the obsolete variable.  Either un-obsoleting this variable, 
> or having the internal file-lock code call (system-name), so it can be 
> overridden with advice, is a suggested solution.

Or you can set system-name to the nil value.