The parser to split up repo and archive name into all needed parts is rather complex.

Also, some commands (prune) have a separate --prefix argument, which is kind of archivename*.

The repo part can also come from BORG_REPO env var.

Native windows support (see "windows branch") might even make it more complex, due to different matching patterns needed for it.

So, if we refactor this (which is a major cli api change, this the 2.0 milestone), it could look like:

borg --repo REPO --archive ARCHIVE command
borg --repo REPO --archive-match ARCHIVE_PATTERN command

ARCHIVE_PATTERN would support glob patterns on the archive name.

Additionally to --archive-match, we could support a --index [from:to] option that just results into that part of the match result list.

Support getting REPO and ARCHIVE from the environment.