Support SSH Git URLs for authenticated connections to private repositories

[jiangliu]

Cargo supports ssh git URLs, but the libgit2 library depends on ssh-agent to handle ssh authentication.
Could we add openssh-server to support ssh git URLs?

[andreeaflorescu]

Where would this be used? We can add it, I just want to understand why we would need it.

[jiangliu]

Often we need to clone rust-vmm crates, make local changes, integrate the modifications with other components and eventually send out PRs to rust-vmm crates. The internal repository are ssh based and we want use the rust-vmm-container to support the dev process.