### Please describe the problem.

After upgrading Debian Buster to Bullseye (and thus git-annex to 8.20210223-2), two sync `git annex sync --content` jobs have started failing.

One is to an encrypted remote:

    sending incremental file list
    54c/e47/
    54c/e47/GPGHMACSHA1--REDACTED/
    54c/e47/GPGHMACSHA1--REDACTED/GPGHMACSHA1--REDACTED
    
             32,768   8%    0.00kB/s    0:00:00
            375,589 100%  326.94MB/s    0:00:00 (xfr#1, to-chk=0/5)
    
    failed
      content changed while it was being sent
      content changed while it was being sent
    git-annex: sync: 1 failed

The content hasn't changed as far as I know.

Another is to another local filesystem (from ext4 to ext4):

```
  failed to send content to remote                                                                                                                                                            
  failed to send content to remote                                                                                                                                                            
  failed to send content to remote                                                                                                                                                            
To /path/to/remote                                                                                                                                                                  
   XXXXXXXXX..XXXXXXXXX  git-annex -> synced/git-annex                                                                                                                                        
   XXXXXXXXX..XXXXXXXXX  master -> synced/master                                                                                                                                              
git-annex: sync: 884 failed        
```

In the latter case, `--debug` prints two ExitFailures:

```
[2021-09-04 13:21:26.943294346] process [2934668] read: cp ["--reflink=always","--preserve=timestamps",".git/annex/objects/gM/mZ/SHA256E-REDACTED.pdf/SHA256E-REDACTED.pdf","/path/to/remote/.git/annex/tmp/SHA256E-REDACTED.pdf"]                                                                                                                                           
[2021-09-04 13:21:26.944187444] process [2934668] done ExitFailure 1
<clip>
2021-09-04 13:21:52.79239764] process [2936730] read: git ["--git-dir=.git","--work-tree=.","--literal-pathspecs","push","remote","master"]                                                  
[2021-09-04 13:21:52.808201959] process [2936730] done ExitFailure 1
```

Manually running that cp command fails with "Permission denied", because the tmp file now exists and has 444 permissions.

### What steps will reproduce the problem?

I haven't tried to reproduce this from a clean repository, but it happens 100 % of the time.

### What version of git-annex are you using? On what operating system?

git-annex 8.20210223-2 on Debian 11/Bullseye.

### Please provide any additional information below.

### Have you had any luck using git-annex before? (Sometimes we get tired of reading bug reports all day and a lil' positive end note does wonders)

These sync worked fine before upgrade.

> [[fixed|done]] in git-annex 8.20210803 --[[Joey]]
