Have you checked borgbackup docs, FAQ, and open GitHub issues?

Yes

Is this a BUG / ISSUE report or a QUESTION?

BUG

System information. For client/server mode post info for both machines.

Your borg version (borg -V).

borg 1.4.0

Operating system (distribution) and version.

NixOS/nixpkgs@5d67ea6

Hardware / network configuration, and filesystems used.

tmpfs

How much data is handled by borg?

kilobytes

Full borg commandline that lead to the problem (leave away excludes and passwords)

borg extract --dry-run --list /var/tmp/borg/::foo 'a*'

Describe the problem you're observing.

I tried to extract multiple files that have the same prefix. The simplest method to achieve this in my mind would be to use a wildcard. According to #361, wildcards should be supported by borg but there is no documentation on it (:/) and they evidently do not work.

Am I doing something wrong? Are users expected to understand and create borg-specific patterns instead to achieve this sort of thing?

Can you reproduce the problem? If so, describe how. If not, describe troubleshooting steps you took before opening the issue.

1. touch a aa aaa
2. borg create /var/tmp/borg/::foo .
3. borg extract --dry-run --list /var/tmp/borg/::foo 'a*'

Include any warning/errors/backtraces from the system logs

Include pattern 'a*' never matched.