When trying to use mv to rename a file on an external drive using coreutils
8.30-2 on a debian system (Linux version 4.19.0-3-amd64), the rename fails
with the error message:

    mv: cannot move 'file1' to a subdirectory of itself 'file2'

Downgrading to coreutils 8.30-1, the rename executes as expected.

The following is the result of running a test script. The folder '/backup'
is an external drive using the ZFS fileystems (zfs-zed 0.7.12-3), but I
have seen a report on superuser.com (
https://superuser.com/questions/1409618/renaming-a-file-with-mv-cannot-move-to-a-subdirectory-of-itself)
that this also happens with NTFS external drives.

root@capella:~# ./mv-bug
+ apt install -y --allow-downgrades coreutils=8.30-1
Reading package lists... Done
Building dependency tree
Reading state information... Done
coreutils is already the newest version (8.30-1).
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
+ cd /backup
+ touch t
+ ls s t
ls: cannot access 's': No such file or directory
t
+ mv t s
+ ls s t
ls: cannot access 't': No such file or directory
s
+ rm s t
rm: cannot remove 't': No such file or directory
+ cd /root
+ apt install -y coreutils=8.30-2
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages will be upgraded:
  coreutils
1 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
Need to get 2,707 kB of archives.
After this operation, 4,096 B disk space will be freed.
Get:1 http://ftp.uk.debian.org/debian sid/main amd64 coreutils amd64 8.30-2
[2,707 kB]
Fetched 2,707 kB in 1s (2,729 kB/s)
apt-listchanges: Reading changelogs...
(Reading database ... 226704 files and directories currently installed.)
Preparing to unpack .../coreutils_8.30-2_amd64.deb ...
Unpacking coreutils (8.30-2) over (8.30-1) ...
Setting up coreutils (8.30-2) ...
Processing triggers for install-info (6.5.0.dfsg.1-4+b1) ...
Processing triggers for man-db (2.8.5-2) ...
+ cd /backup
+ touch t
+ ls s t
ls: cannot access 's': No such file or directory
t
+ mv t s
mv: cannot move 't' to a subdirectory of itself, 's'
+ ls s t
ls: cannot access 's': No such file or directory
t
+ rm s t
rm: cannot remove 's': No such file or directory
root@capella:~#