@mcc my understanding is the workspace would be defined in the submodule, so that when you call cargo *in that submodule*, it will only read submodule/.cargo/config.toml
similarly, submodule/.cargo/config.toml values take precedence over root/.cargo/config.toml
so if it were:
root/.cargo/config.toml::[build] jobs = 2
that was breaking things, you would override with:
root/submodule/.cargo/config.toml::[build] jobs = 1