Repository should provide a "fix" utility

[smoelius]

The repository should provide a method that a client repository could all in a #[test].

In that way, client repositories wouldn't have to store a copy of clippy_conf/clippy.toml.

A test that stores a copy of clippy_conf/clippy.toml now: https://github.com/smoelius/nested_workspace/blob/2fe37d79d44d67aa8e64b366afca0dbb5ea53f40/tests/ci.rs#L66-L79

[smoelius]

It would also be nice to have a "fix" utility.

Ideally, one with a --aggressive option that removes .with_context(..) calls following a rewritten function.

[smoelius]

Renamed to 'provide a "fix" utility" since a disallowed_tests function was merged: #118