Cosign "save" and "load" commands

[dlorenc]

We should add some commands to save an image and it's "attachments" to disk in some kind of bundle on disk, and then load that into a remote registry from disk. See this thread: https://twitter.com/sudo_bmitch/status/1457794784135761920

[dlorenc]

cc @developer-guy this could be a fun one :)

[priyawadhwa]

chatted with @developer-guy, i might give this a go! :)

[developer-guy]

I assigned it to you @priyawadhwa. Thank you so much for asking it me first, that was very kind! Good luck with it. We can't wait to see the results! 🚀

[dlorenc]

What's left here @priyawadhwa? This one would be great for the next release.

[priyawadhwa]

hoping to have a PR open by tmrw! just have to hook up the commands to the layout package (currently seeing a bug with writing to a remote repo tho so just have to get to the bottom of that)

[priyawadhwa]

it might be useful to add support for the layout on disk to cosign verify -- maybe something like cosign verify -key [KEY] [path to image directory]?

[haydentherapper]

Chatted with @priyawadhwa about working on #1015 (comment) to add support for verification from disk. I'll be taking a look at adding this!