Why is there .cargo/config.toml file?

[dsabala]

Hi

Coming from C language, CMake build-system and PyInvoke project CLI support I am really impressed by how Rust treats build-system issues. However I cant understand why we use .cargo/config.toml files so extensively in the first place?

According to the Cargo documentation, the .cargo/config.toml file is a kind of hierarchical Cargo configuration. How can we define e.g. the target target.thumbv7m-none-eabi in such a file?

Why cant we move all content from .cargo/config.toml to manifest file Cargo.toml ?

Edit:

I guess this choice is made to keep Cargo.toml file more platform-generic?
I think that it could be explained inside this .cargo/config.toml file

Edit 2:

Rust and Cargo are still evolving, it looks like .cargo/config.toml file was there before introduction of Cargo.toml file and now there are ongoing works to move some configuration to Cargo.toml file

rust-lang/cargo#12738