Separate licenses with a / instead of OR

[CAD97]

It's what we tell others to do.

https://doc.rust-lang.org/cargo/reference/manifest.html#package-metadata

# This is a string description of the license for this package. Currently
# crates.io will validate the license provided against a whitelist of known
# license identifiers from http://spdx.org/licenses/. Multiple licenses can be
# separated with a `/`.
license = "..."

Noted here.

This should either use / or a note should be added that OR is allowed as a combination operator.

[rust-highfive]

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[alexcrichton]

@bors: r+

[bors]

📌 Commit 1ddba76 has been approved by alexcrichton

[bors]

⌛ Testing commit 1ddba76 with merge ed8dfce...

[bors]

☀️ Test successful - status-appveyor, status-travis
Approved by: alexcrichton
Pushing ed8dfce to master...

[ehuss]

I think this is the opposite of what others have been transitioning towards. #4898 explicitly marked / as being deprecated.

[matklad]

Yeah, it seems @ehuss is right! #4920 switched / to OR some time back =P

I wonder if we should implement a warning on cargo publish

[ehuss]

@matklad I can't find an explicit issue for issuing deprecation warnings, but I think the intent is to do that, but is maybe stalled on updating the license API to get those warnings? @wking may know more about that.

[wking]

I think we want to revert this change and return to the SPDX-specified OR instead of the deprecated, Cargo-specific /.

I can't find an explicit issue for issuing deprecation warnings, but I think the intent is to do that, but is maybe stalled on updating the license API to get those warnings?

There's some discussion of warning in #2039. And yeah, license-exprs would need to grow an API that allowed reporting warnings (slightly more on that around here). license-exprs seems to still be stuck in a maintainer transition though (ehuss/license-exprs#12), so it may be a while before it grows such an API.

[matklad]

Aaaaand switching this back to OR in #5080 :)

[CAD97]

My bad, mayhaps update the documentation in prod :)