bug#69532: mv's new -x option should be made orthogonal to -t/-T/default

[Rob Landley]

On 3/4/24 18:43, Dominique Martinet wrote:
> Adding Rob to the loop because this impacts compatibility with
> toybox/maybe busybox implementations
> (Quoting in full for convenience, there's a few more mails in
> https://lists.nongnu.org/archive/html/bug-coreutils/2024-03/msg00002.html
> but we seem to be missing Petr's reply)
> 
> Pádraig Brady wrote on Mon, Mar 04, 2024 at 03:47:23PM +0000:
>> On 04/03/2024 00:44, Paul Eggert wrote:
>> > Although I like the idea of exposing file swaps to the user, the first
>> > cut of 'mv -x' has significant problems.
>> > 
>> > I expect 'mv -x A B' to act like 'mv A B' except the destination must
>> > exist and is renamed back to A. However, this is not true for 'mv -x A
>> > B' when B is a directory; it renames B to A rather than renaming B/A to
>> > A as I expect.

I don't expect that. I expect it to swap the two. I don't care if one is a
directory and the other is a symlink or file or device node or what.

I asked it to swap A and B. It did that. If I wanted to ask it to swap with B/A
I could have said so.

>> > That is, 'mv -x' acts as if -T (--no-target-directory) is
>> > also specified.

Then document that?

>> Also if we made this change, We'd have to document that `mv -x 1 2 ... d`
>> was not atomic over the whole set.

Making the atomic exchange not be atomic kind of defeats the purpose...

Rob