bug#10489: 24.0.92; dired-do-copy may create infinite directory hierarchy

[Stefan Monnier]

>>> I have modified files-equal-p and file-subdir-of-p to work with
>>> non--existing files,
>> Calling files-equal-p on non-existing files makes no sense, so I don't
>> think we should support it (at least not until we have concrete
>> evidence that it is needed, at which point we can decide what we intend
>> it to mean).
> It is useful to handle e.g
> (copy-directory "~/test" "~/test/test1")
> where test1 is a non--existing directory.

I see why we might want to signal an error to the user when she does
(copy-directory "~/test" "~/test/test1"), but I don't see why that
implies that we need files-equal-p to handle non-existent files.


        Stefan