--message-format is released ahead of time

[White-Oak]

Message formats introduced in #3000 were supposed to be in the next stable release (see this comment).

But it looks like it jumped from nightly to stable immediately. Is is this supposed to be so?

[alexcrichton]

Yeah we unfortunately had to accelerate the Cargo release due to releasing the curl/OpenSSL security fixes. As a result other features landed before that were included implicitly as well.