Typos in badge names aren't caught by cargo publish --dry-run

[daboross]

Problem

If I make a typo in the badges portion of my cargo library, there's no warning on compile nor on a dry-run publish, and I only get to see that something's wrong after the publish succeeds.

Steps

1. Create a new cargo library.
2. Add to Cargo.toml:

[badges]
is-it-mantained-issue-resolution = { repository = "daboross/fern" }

3. Try to catch publish errors using cargo publish --dry-run (no errors are displayed)
4. Publish the crate on crates.io using cargo publish (this displays a warning about is-it-mantained-issue-resolution being ignored as a badge)

Possible Solution(s)

I'd expect this should be possible by pinging the crates.io servers on a dry-run upload to check whether there are any invalid attributes. I expect cargo publish --dry-run to do everything that cargo publish does short of actually publishing it, so if there's a step separate from uploading that cargo publish does to display errors about ignored badges, maybe it could do that?

Notes

Output of cargo version: cargo 1.43.0-nightly (e57bd0299 2020-02-21)

[ehuss]

Eventually we would like to have a new publish API that supports this. Since this is already reported in #3576, closing as a duplicate.