Prepare 2.2.0

[ctz]

Release notes:

The main function of this crate has been incorporated into rustls-pki-types. 2.2.0 maintains the existing public API for this crate, on top of this new implementation. This drops the dependency on the base64 crate, and allows for constant-time decoding of private keys.

This crate will continue to exist in its current form, but it is somewhat unlikely that the API will be extended from its current state.

Should you wish to migrate to using the new rustls-pki-types PEM APIs directly, here is a rough cheat-sheet:

Use case	Replace
File stream to CertificateDer iterator	rustls_pemfile::certs(io::BufRead) ➡️ CertificateDer::pem_reader_iter(io::Read)
File stream to one PrivateKeyDer	rustls_pemfile::private_key(io::BufRead) ➡️ PrivateKeyDer::from_pem_reader(io::Read)
File stream to one CertificateSigningRequestDer	rustls_pemfile::csr(io::BufRead) ➡️ CertificateSigningRequestDer::from_pem_reader(io::Read)
File stream to CertificateRevocationListDer iterator	rustls_pemfile::crls(io::BufRead) ➡️ CertificateRevocationListDer::pem_reader_iter(io::Read)
File stream to PrivatePkcs1KeyDer iterator	rustls_pemfile::rsa_private_keys(io::BufRead) ➡️ PrivatePkcs1KeyDer::pem_reader_iter(io::Read)
File stream to PrivatePkcs8KeyDer iterator	rustls_pemfile::pkcs8_private_keys(io::BufRead) ➡️ PrivatePkcs8KeyDer::pem_reader_iter(io::Read)
File stream to PrivateSec1KeyDer iterator	rustls_pemfile::ec_private_keys(io::BufRead) ➡️ PrivateSec1KeyDer::pem_reader_iter(io::Read)
File stream to SubjectPublicKeyInfoDer iterator	rustls_pemfile::public_keys(io::BufRead) ➡️ SubjectPublicKeyInfoDer::pem_reader_iter(io::Read)

[ctz]

(maybe this big table isn't warranted in the release notes, maybe the README instead?)

[cpu]

Release notes LGTM.

Should you wish to migrate to using the new rustls-pki-types PEM APIs directly, here is a rough cheat-sheet:

Maybe hyperlink to https://github.com/rustls/pki-types or https://docs.rs/rustls-pki-types/latest/rustls_pki_types/ ?

(maybe this big table isn't warranted in the release notes, maybe the README instead?)

I don't think there's a big disadvantage to having it in the release notes (or both places!).

[cpu]

maybe the README instead

It would probably be a good idea to include a paragraph in the README about the future of this crate/API in either case

[ctz]

Maybe hyperlink to https://github.com/rustls/pki-types or https://docs.rs/rustls-pki-types/latest/rustls_pki_types/ ?

Linked.

README

Added.

[djc]

Nice!