The borg special remote allows git-annex to treat borg backups of a git-annex repository as just another remote. This could also be done for other backup software.

restic seems like a good candidate. What other commonly used backup software might be good to support? Comments welcome with suggestions..

Currently, support for these has to be in git-annex, it cannot be an external special remote. Just providing a way to in the external special remote interfase to set thirdPartyPopulated might be enough to allow using external special remotes for this.

The borg implementation does have getImported which looks at the git-annex branch, and is used in an optimisation. It would be good to factor that out to a common optimisation for all thirdPartyPopulated remotes. --Joey