New Rustdoc can't document individual rs files

[euclio]

I think there's a bit of an mismatch between the fact that old rustdoc allows documenting individual files while the new rustdoc expects a crate with Cargo.toml. How do we want to handle that?

Another way of putting it is that the old rustdoc expects to be wrapped by cargo, while the new rustdoc expects to wrap cargo.

cc #125

[steveklabnik]

[euclio]

Are we talking about the same thing? I originally opened the issue intending to talk about individual Rust files, not markdown. You can invoke the old rustdoc like rustdoc some_file.rs and it will create documentation for that file, without needing a Cargo.toml. Not saying we need to support that use case, but I'd like us to make an official decision.

[steveklabnik]

Oh!

Since that's just a crate root, yeah, okay. Let me change the title again; I misunderstood.