No backup when using %F in the snapshot-format

[Grinzold]

I tried using the time format %F, which is a shortcut for %Y-%m-%d:

> date +%F; date +%Y-%m-%d
2025-01-30
2025-01-30

When using %F the snapshots are created OK, but nothing gets backed up.

Furthermore the return value is 0, so no problem is reported!

As a workaround using %Y-%m-%d instead of %F does the job. So, one could check for %F in the format and

• output an error message, or
• (silently) replace it with '%Y-%m-%d'

The actual format I used was --snapshot-format "{}_%F_%H%M%S", which did not work.

BTW, for testing it would be really helpful to just specify a snapshot as a source, instead of a backup-name and setting the corresponding property...