git-annex backend

[wlandau]

Prework

Prework

• [x] Read and agree to the Contributor Code of Conduct and contributing guidelines.
• [x] If there is already a relevant issue, whether open or closed, comment on the existing thread instead of posting a new issue.
• [x] New features take time and effort to create, and they take even more effort to maintain. So if the purpose of the feature is to resolve a struggle you are encountering personally, please consider first posting a "trouble" or "other" issue so we can discuss your use case and search for existing solutions first.
• [x] Format your code according to the tidyverse style guide.

Description

• https://git-annex.branchable.com
• Unlike git-lfs, git-annex uses a different command line interface than standard Git, so we may need special new tar_git_annex_*() functions in gittargets.

[wlandau]

The intent of git-annex seems to be storing the files in a different non-cloud location, which is not really a good fit for targets. Plus, there's the fact that LFS is more popular than Annex. Closing for now.