change ssh private key default to ed25519 before checking for rsa

[jashandeep-sohi]

Currently, only RSA keys are supported:

cargo-generate/src/git.rs

Line 119 in 528bf38

let private_key = identity.unwrap_or(home()?.join(".ssh/id_rsa"));

However, more and more people are defaulting to ed25519(myself included). Having to setup a rsa key just for cargo-generate is not ideal.

cargo-generate should at least support ed25519 keys as well.

Edit: I realize I could manually override this via -i | --identity, but my request is to make it automatically use id_ed25519 if it exists.

[sassman]

My proposal would be to try a couple of defaults and what ever is there will be used. With this given order:

• RSA id_rsa
• ed25519

Anything else that folks are using that is not mentioned in the list above?

[jashandeep-sohi]

This also got me thinking about something else. What happens when keys are password protected (or more recently require a security key to unlock). Wouldn't it just be better to delegate all of this to ssh-agent via https://docs.rs/git2/0.7.5/git2/struct.Cred.html#method.ssh_key_from_agent or any credential helper via https://docs.rs/git2/0.7.5/git2/struct.Cred.html#method.credential_helper

[sassman]

those are very valid points. I'll toy around with them in order to understand the behaviour in cases there no ssh-agent is running or the credential helper fails to figure things out.

But I guess we can extend the scope of this issue to support also arbitrary protected private keys, not only elliptic curve keys.