Thank you for filling out a Git bug report!
Please answer the following questions to help us understand your issue.

What did you do before the bug happened? (Steps to reproduce your issue)
Running the following script (test.sh) multiple times:

 ```
 #!/bin/bash
GIT_TRACE=true
export GIT_TRACE

mkdir gitDir0
cd gitDir0
env git -c init.defaultBranch=master init 
echo bar > bar.txt
env git add -v bar.txt 
env git -c user.name="P" -c user.email="e@mail.com" commit -v -m first 

mkdir ../gitDir2
cd ../gitDir2
env git -c init.defaultBranch=master init 
env git pull -v --set-upstream ../gitDir0 
echo foo > foo.txt
env git add -v foo.txt 
env git mv -v -f -- foo.txt bar.txt 
env git reset --merge HEAD
```

What did you expect to happen? (Expected behavior)
I expect that the script shows the same behavior on every execution.

What happened instead? (Actual behavior)
I encountered two different behaviors (random):
1. Most of the time the git reset command succeeds and the file gitDir2/bar.txt contains the string "bar" after running the script.
2. Sometimes the git reset command fails and the file gitDir2/bar.txt contains the string "foo" after running the script.
In this case, the reset command produces the following output:
```
error: Entry 'bar.txt' not uptodate. Cannot merge.
fatal: Could not reset index file to revision 'HEAD'.
```
The full console output of both cases is attached to this mail, but they only really differ in this error message.

Anything else you want to add:
I could observe this behavior on git 2.35.1 and 2.34.1.
The behavior is not affected by whether GIT_TRACE is set.

I wrote a script that executes this test script repeatedly and keeps track of the possible outcomes of the gitDir2/bar.txt file.
It will print a line each time the content differs from the previous execution.
This script is attached to this mail (runner.sh).
Sample output of this script:
```
execution #0 	 hash: c157a79031e1c40f85931829bc5fc552 	 date: Thu Mar 24 13:22:17 UTC 2022
execution #203 	 hash: d3b07384d113edec49eaa6238ad5ff00 	 date: Thu Mar 24 13:22:29 UTC 2022
execution #204 	 hash: c157a79031e1c40f85931829bc5fc552 	 date: Thu Mar 24 13:22:29 UTC 2022
execution #264 	 hash: d3b07384d113edec49eaa6238ad5ff00 	 date: Thu Mar 24 13:22:32 UTC 2022
execution #265 	 hash: c157a79031e1c40f85931829bc5fc552 	 date: Thu Mar 24 13:22:32 UTC 2022
execution #432 	 hash: d3b07384d113edec49eaa6238ad5ff00 	 date: Thu Mar 24 13:22:40 UTC 2022
execution #433 	 hash: c157a79031e1c40f85931829bc5fc552 	 date: Thu Mar 24 13:22:40 UTC 2022
execution #489 	 hash: d3b07384d113edec49eaa6238ad5ff00 	 date: Thu Mar 24 13:22:43 UTC 2022
```


[System Info]
git version:
git version 2.35.1
cpu: x86_64
built from commit: 4c53a8c20f8984adb226293a3ffd7b88c3f4ac1a
sizeof-long: 8
sizeof-size_t: 8
shell-path: /bin/sh
uname: Linux 5.10.25-linuxkit #1 SMP Tue Mar 23 09:27:39 UTC 2021 x86_64
compiler info: gnuc: 10.2
libc info: glibc: 2.31
$SHELL (typically, interactive shell): <unset>


[Enabled Hooks]
not run from a git repository - no hooks to show