add crate_authors! macro

[rtaycher]

Once rust-lang/cargo#2465 lands it would be useful to have a crate_authors! macro to complement the crate_version! macro (fetch authors from cargo).

It's a pretty small change.

master...rtaycher:add_authors_macro

But it won't work on old cargo binaries.

Should I put this behind feature flags(at first)?

[kbknapp]

Awesome idea! I'm ok with not using feature flags, so long as the minimal version of cargo for this macro is annotated in the documentation. Thanks 👍

[sru]

Since the environment variable is new, we could provide two versions of macros: One is just using env! (which will emit compilation error if the environment variable is not found), and other using option_env! and let user provide default authors if the environment variable is not found.

[rtaycher]

I thought about using option_env! instead but then you get something that will need to be deprecated or be awkward later on.

Also to clarify technically it's newer then new, it hasn't been merged yet though I think it will be soon. I was thinking about adding a feature flag then dropping the flag after a year.

[sru]

@rtaycher I guess it can get awkward after a while.

Once the pr is merged, can you amend the commit messages to follow the contribution guideline and make a pull request?

[kbknapp]

So yeah let's us a feature flag until it's in stable Rust. Whether that's the unstable flag or another one devoted to just this feature is the same to me.

[TheNeikos]

I find it funny, it's exactly for this use case that I proposed that change on rust/cargo 😄