Fix default credentials location

[HomyeeKing]

No description provided.

[Turbo87]

hmm, https://doc.rust-lang.org/cargo/reference/config.html says that the path is $CARGO_HOME/credentials.toml. why do you want to remove the .toml suffix?

/cc @rust-lang/cargo

[weihanglo]

Files without .toml extension exist for backward compatibility. IIRC Cargo team encourages the use of credentials.toml. See also https://github.com/rust-lang/cargo/blob/74c7aab19a9b3a045e7af13319409a9de2cf4ef7/src/cargo/util/config/mod.rs#L1400-L1404

The purpose of this function is to aid in the transition to using
.toml extensions on Cargo's config files, which were historically not used.
Both 'config.toml' and 'credentials.toml' should be valid with or without extension.
When both exist, we want to prefer the one without an extension for
backwards compatibility, but warn the user appropriately.

[HomyeeKing]

in which cargo version add .toml suffix？ mine is argo 1.65.0 (4bc8f24d3 2022-10-20)
because I do cargo login <token> today then I want to check if the token was stored, but the ~/.cargo/credentials.toml
is not exist.
I only found ~/.cargo/credentials, maybe the docs should display like ~/.cargo/credentials[.toml]

[weihanglo]

From here rust-lang/cargo#7295 since 1.39, specifically this comment. However, the transition period was not what I expected or not finished. Feel like Cargo should by default write to credentials.toml.

I'd suggest transferring this to rust-lang/cargo. Cargo then can do such enhancements:

• File a patch writing to credentials.toml if credentials doesn't exist.
• Document the fallback behavior properly.
• rust-lang/crates.io could cross-link to cargo doc to avoid doc duplicate.

I have no enough information of why it designed like that. Could bring it up to the next triage meeting (though most of the team are on vacation 🏝).

[Turbo87]

merging this for now until cargo is updated to actually generate credentials.toml by default :)