Incorrect warning about README outside package

[djc]

Problem

When publishing quinn 0.10.0 from quinn-rs/quinn@a66ee19, I get the following warning:

djc-2021 main quinn $ cargo publish # here the current working directory is the inner quinn dir for the crate, not the repo root
    Updating crates.io index
warning: readme `../README.md` appears to be a path outside of the package,
but there is already a file named `README.md` in the root of the package.
The archived crate will contain the copy in the root of the package. Update the
readme to point to the path relative to the root of the package to remove this warning.

This is confusing because "there is already a file named README.md in the root of the package" doesn't match my understanding. The repository contains a /README.md which is at the root of the workspace, but there's no /quinn/README.md in the package.

The archived crate will contain the copy in the root of the package.

This also doesn't appear to be true -- the repo-root/workspace-root ../README.md appears on crates.io just fine.

Update the readme to point to the path relative to the root of the package to remove this warning.

This is what we already have?

Version

djc-2021 main quinn $ cargo version --verbose
cargo 1.68.0 (115f34552 2023-02-26)
release: 1.68.0
commit-hash: 115f34552518a2f9b96d740192addbac1271e7e6
commit-date: 2023-02-26
host: aarch64-apple-darwin
libgit2: 1.5.0 (sys:0.16.0 vendored)
libcurl: 7.87.0 (sys:0.4.59+curl-7.86.0 system ssl:(SecureTransport) LibreSSL/3.3.6)
os: Mac OS 13.3.1 [64-bit]

[ehuss]

Looks like this is caused by having another README.md file located in examples/README.md. There is a flaw in how Cargo checks for a conflict here. That should not use file_name().

[eval-exec]

Hello, @ehuss @djc . I linked a #12135 to solve this issue, please review the fix and unit tests. 💟

Do you think I need to add additional unit tests?

[djc]

@eval-exec thanks for looking at this! I don't have strong opinions on your work, but very happy that this is quickly getting fixed.