Error message with `credential-process` and a `token` is confusing.

[ehuss]

Problem

If you are currently logged in to a registry using the typical token setting in credentials.toml, and you add a configuration for registry.credential-process, the error message when running cargo login is a little confusing:

error: both `token` and `credential-process` were specified in the config.
Only one of these values may be set, remove one or the other to proceed.

If a user is not following the instructions to the letter, or is not intimately familiar with cargo's auth setup, this doesn't really tell you what to do to fix the error.

Steps

1. Do a normal login: cargo login
2. Set up a credential process in config.toml:

   [registry]
   credential-process = "cargo:1password"

3. Run cargo login -Zcredential-process

Possible Solution(s)

The error message could be a little clearer about what it means about a "token...in the config". A user may not know or equate that a legacy cargo login means that a "token is in the config". I would probably completely reword this error message to explain that they are logged in via the old mechanism, and that needs to be removed before using credential-process (though I'm not sure how to phrase "old mechanism").

I think the message could also include some instructions on how to fix it (such as running cargo logout).

Notes

No response

Version

cargo 1.72.0-nightly (03bc66b55 2023-06-23)
release: 1.72.0-nightly
commit-hash: 03bc66b55c290324bd46eb22e369c8fae1908f91
commit-date: 2023-06-23
host: aarch64-unknown-linux-gnu
libgit2: 1.6.4 (sys:0.17.2 vendored)
libcurl: 8.1.2-DEV (sys:0.4.63+curl-8.1.2 vendored ssl:OpenSSL/1.1.1u)
ssl: OpenSSL 1.1.1u  30 May 2023
os: Ubuntu 22.04 (jammy) [64-bit]

[chansuke]

@rustbot claim

[arlosi]

@chansuke FYI I'm making significant changes to how -Zcredential-process works in #12334.

[ehuss]

I'm going to close as resolved by #12334. The new behavior is to issue a warning that looks like:

warning: registry `crates-io` has a token configured in /Users/eric/.cargo/credentials.toml that will be ignored because the `cargo:token` credential provider is not listed in `registry.global-credential-providers`

This points the user to the file where the token is, and explains why it is not being used. Hopefully that provides enough information for the user to figure out what to do, but we can definitely iterate on it more if it isn't clear enough.