bug#39057: 27.0.60; copy-file interactive VS from lisp disagreement

[Eli Zaretskii <eliz@gnu.org>]

> From: Tino Calancha <tino.calancha@gmail.com>
> Date: Thu, 09 Jan 2020 22:03:19 +0100
> 
> Observed a disagreement when calling `copy-file' interactively VS calling
> it from Lisp.
> 
> This is a recipe:
> 
> ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
> emacs -Q:
> $ touch /tmp/foo
> M-x copy-file RET /tmp/foo RET ~/ RET
> ;; Received prompt:
> ;; File /home/calancha already exists; copy to it anyway? (y or n) 

I cannot reproduce this, so there must be more here than meets the
eye, like whether /tmp/foo existed before the 'touch' command (and if
so, what kind of file is it and what are its attributes), the contents
of your home directory that could have something to do with this, etc.

So please step through the code and tell where it fails and why.
Alternatively, try reproducing this in a cleaner environment (a home
directory and /tmp could have a lot of files), and see if something
changes then.

Or maybe you didn't actually type the slash in "~/" when invoking the
command interactively?

Thanks.