mv: show "same file" error for mv d/f d

[cakebaker]

When using mv d/f d, GNU mv fails with a "same file" error whereas uutils mv doesn't fail. This PR makes uutils mv fail, too.

[samueltardieu]

I wonder if this is the right fix. GNU mv fails at moving t/a into u/b if u/b exist and is the same file as t/a (hard link), while your patch seems to compare parents.

Reproducer:

$ mkdir t u
$ touch t/a
$ ln t/a u/a
$ mv t/a u
mv: 't/a' and 'u/a' are the same file

With your patch:

$ […]/target/debug/coreutils mv t/a u
[success]

[cakebaker]

Thanks for your feedback. I didn't consider hard links when creating this PR :|

[samueltardieu]

I think you can reuse/move around most of the code just before your patch. IIRC, it checks for hardlink equivalence when the target is a file, so if you build the target file name in case you get a directory I guess you might use the same check.

[sylvestre]

@cakebaker ping ? :)

[github-actions]

GNU testsuite comparison:

Congrats! The gnu test tests/mv/mv-n is no longer failing!
Congrats! The gnu test tests/mv/update is no longer failing!
Skipping an intermittent issue tests/tail/inotify-dir-recreate (passes in this run but fails in the 'main' branch)

[sylvestre]

sorry, i missunderstood, it, reverting it

[sylvestre]

please reopen when ready :)