Backup exporter

[OpenBagTwo]

GIVEN Steve wants to export a specific backup of a specific save state (my-save) at a specific time AND he doesn't want that export to include the full history attached

WHEN he runs the command gsb export my-save [tag-name-or-commit-hash] (or omits that argument to just use the current state)

THEN a file should be generated in the current working directory named my-save.<tag-name-or-commit-hash>.zip* containing a static snapshot of the specified backup

SO that he can take that export and use it on another machine, upload it to a bug-tracker for diagnostics, safely dissect it, or put it into some cold storage medium without having to run the git command manually

Notes

• Under the hood, this is git archive
• This action should also accept the flags --filename and --format (passing through to --output and --format, respectively
• *I'm actually in favor of Linux systems getting .tar.xz by default

[OpenBagTwo]

So pygit2's write_archive method only supports tarfiles. This means that in order to support zip gsb will either:

1. need to convert a tarball to a zip archive
2. create a translation wrapper around ZipFile that implements the tarfile methods called by write_archive
3. Implement my own write_archive

I was originally thinking about (2), but honestly that's going to be extremely brittle unless I pin the version of pygit2.