This is the result of running cargo clippy on hg-core/hg-cpython and fixing
the lints that do not require too much code churn (and would warrant a separate
commit/complete refactor) and only come from our code (a lot of warnings in
hg-cpython come from rust-cpython).
Most of those were good lints, two of them was the linter not being smart
enough (or compiler to get up to clippy's level depending on how you see it).
Maybe in the future we could have clippy be part of the CI.