feat(ssh-git): Introduce support to pull repositories using ssh keypairs

[leophys]

Hi folks! I love what you are building and wanted to contribute back. I see a use case where someone (me?) would like to pull private repositories. As of now, this is supported only for forges which accept authentication mechanisms through HTTP. I wanted to support pulling via ssh using ssh keys.

Doing so, I also refactored the code to drop invoking the git binary and instead completely rely on git2-rs, which is already a dependency you were pulling in.

Currently, this PR only includes the backend work. There is also the need for a UI change to make this available for end users, and here I stopped. I did because I understand this is a product, and you might want to have a discussion (open or not) on how (whether) to expose this feature to the users.

I designed the change to allow both keys stored in files and as text in the database. This seemed like a sensible and easy thing to do.

There are three new tests:

• one to test pulling a public repository using the new code path (that leverages only git2-rs)
• two more to try and pull private repository either providing a path to a private key or the private key itself via env variables (these are skipped if the needed environment variables are not set)

I am open for feedback/discussions. I am also keen to do the frontend work, if we agree on a final UX/UI.

[leophys]

I don't know how to ask for a review to a team member, so I am just tagging someone, @gyxlucy

[leophys]

Hi there! 👋
Is there any bandwidth to deal with this? I would really like to add this feature 🙏

[wsxiaoys]

add @zwpaper