Upstream patch on top of coreutils-9.1; remove with >9.1.
Fixes: https://bugs.gnu.org/55029

Two commits:

* https://git.sv.gnu.org/cgit/coreutils.git/commit/?id=e087525091b

  commit e087525091b8f0a15eb2354f71032597d5271599
  Author: Paul Eggert <eggert@cs.ucla.edu>
  Date:   Wed Apr 20 19:44:56 2022 -0700

    mv: test Bug#55029
    
    * tests/mv/backup-dir.sh: New test for Bug#55029,
    reported by Steve Ward.

* https://git.sv.gnu.org/cgit/gnulib.git/commit/?id=7347caeb9d90

  commit 7347caeb9d902d3fca2c11f69a55a3e578d93bfe
  Author: Paul Eggert <eggert@cs.ucla.edu>
  Date:   Wed Apr 20 19:34:57 2022 -0700

    backupfile: fix bug when renaming simple backups
    
    * lib/backupfile.c (backupfile_internal): Fix bug when RENAME
    and when doing simple backups.  Problem reported by Steve Ward in:
    https://bugs.gnu.org/55029

---
 NEWS                   |    8 ++++++++
 lib/backupfile.c       |    7 +++----
 tests/mv/backup-dir.sh |    6 ++++++
 3 files changed, 17 insertions(+), 4 deletions(-)

Index: lib/backupfile.c
===================================================================
--- lib/backupfile.c.orig
+++ lib/backupfile.c
@@ -332,7 +332,7 @@ backupfile_internal (int dir_fd, char co
     return s;
 
   DIR *dirp = NULL;
-  int sdir = AT_FDCWD;
+  int sdir = dir_fd;
   idx_t base_max = 0;
   while (true)
     {
@@ -371,10 +371,9 @@ backupfile_internal (int dir_fd, char co
       if (! rename)
         break;
 
-      int olddirfd = sdir < 0 ? dir_fd : sdir;
-      idx_t offset = sdir < 0 ? 0 : base_offset;
+      idx_t offset = backup_type == simple_backups ? 0 : base_offset;
       unsigned flags = backup_type == simple_backups ? 0 : RENAME_NOREPLACE;
-      if (renameatu (olddirfd, file + offset, sdir, s + offset, flags) == 0)
+      if (renameatu (sdir, file + offset, sdir, s + offset, flags) == 0)
         break;
       int e = errno;
       if (! (e == EEXIST && extended))
Index: tests/mv/backup-dir.sh
===================================================================
--- tests/mv/backup-dir.sh.orig
+++ tests/mv/backup-dir.sh
@@ -36,4 +36,10 @@ mkdir C D E || framework_failure_
 mv -T --backup=numbered C E/ || fail=1
 mv -T --backup=numbered D E/ || fail=1
 
+# Bug#55029
+mkdir F && echo 1 >1 && echo 2 >2 && cp 1 F/X && cp 2 X || framework_failure_
+mv --backup=simple X F/ || fail=1
+compare 1 F/X~ || fail=1
+compare 2 F/X || fail=1
+
 Exit $fail
Index: NEWS
===================================================================
--- NEWS.orig
+++ NEWS
@@ -1,5 +1,13 @@
 GNU coreutils NEWS                                    -*- outline -*-
 
+* Downstream changes on top of release 9.1
+
+** Bug fixes
+
+  'mv --backup=simple f d/' no longer mistakenly backs up d/f to f~.
+  [bug introduced in coreutils-9.1]
+
+
 * Noteworthy changes in release 9.1 (2022-04-15) [stable]
 
 ** Bug fixes