Allow id_ed25519 keypair name

[weshinsley]

Addresses issue #53

[richfitz]

Thanks - some bits that we might add:

• an item to the NEWS.md file
• check through the vignette and add an explanatory message so that people are not alarmed if their keypair differs
• probably worth in a future issue offering to create these new keys rather than rsa as they are meant to be more secure - probably worth doing that before CRAN release though

[richfitz]

I don't love this bit - particularly that the error is a different sort of thing. Perhaps:

guess_key_error <- function() {
  paste(sprintf("%s[.pub] pair", guess_key()), collapse = " or ")
}

replacing use of guess_key_options(error = TRUE)

Later we might want to generalise this approach and allow setting key priorities?

[weshinsley]

Agree - have separated that out so we have one function providing the list of key-stubs and separate error func...

[weshinsley]

• Above fix done
• News item added
• Vignette refreshed
• The order of filenames in acceptable_key_filenames() currently (crudely) allows for prioritisation should both of the recognised keypairs exist; I'll create separate internal issue for allowing key creation to do the new type.

[weshinsley]

Going back to draft, as it seems from the issue that just detecting the filename is not sufficient