RFC: Cargo feature deprecation

[tgross35]

Rendered

RFC for feature-deprecation RFC goals: add a way to deprecate Cargo features

This was split from https://github.com/rust-lang/rfcs/pull/3416

[features]
foo = { enables = [], deprecated = true }
foo = { enables = [], deprecated = "this works as a note" }
bar = { enables = [], deprecated = { since = "1.2.3", note = "don't use this!" } }

This would resolve https://github.com/rust-lang/cargo/issues/7130