Clarify that edition can be set in a Cargo workspace

[djc]

This seems to work, but is not mentioned in the guide (in transitioning.html):

cargo-features = ["edition"]

[workspace]
members = ["askama", "askama_derive", "askama_shared", "testing"]
edition = "2018"

Obviously, adding it one place instead of per-crate is rather attractive!

[ehuss]

I don't think this is correct. edition is ignored in a virtual manifest. All unknown keys are ignored (there is issue rust-lang/cargo#4243 to add a warning).

[djc]

Hmm, I seem to remember I actually verified that it was doing this. If it's not currently implemented, it would sure be nice to implement.

[steveklabnik]

From IRC:

20:39 < ehuss> @steveklabnik: fwiw, I added a warning a few days ago that the key is ignored.

So, seems like we can close this one.

[Centril]

Hmm... can we make the key not be ignored and actually use it? That seems very useful for larger projects...

[steveklabnik]

That discussion belongs on Cargo's tracker, not here.

[Centril]

That's true :)