message: Add some documentation about unstable namespaced-features feature
diff: @@ -227,3 +227,30 @@ opt-level = 3
  ```
  Overrides can only be specified for dev and release profiles.
  +
  +
  +### Namespaced features
  +* Original issue: [#1286](https://github.com/rust-lang/cargo/issues/1286)
  +
  +Currently, it is not possible to have a feature and a dependency with the same
  +name in the manifest. If you set `namespaced-features` to `true`, the namespaces
  +for features and dependencies are separated. The effect of this is that, in the
  +feature requirements, dependencies have to be prefixed with `crate:`. Like this:
  +
  +```toml
  +[project]
  +namespaced-features = true
  +
  +[features]
  +bar = ["crate:baz", "foo"]
  +foo = []
  +
  +[dependencies]
  +baz = { version = "0.1", optional = true }
  +```
  +
  +To prevent unnecessary boilerplate from having to explicitly declare features
  +for each optional dependency, implicit features get created for any optional
  +dependencies where a feature of the same name is not defined. However, if
  +a feature of the same name as a dependency is defined, that feature must
  +include the dependency as a requirement, as `foo = ["crate:foo"]`.
  