* refactor: Inherit where possible
As recommended by `statix check`.
* refactor: Remove unnecessary parentheses
As recommended by `statix check`.
* refactor: Remove unnecessary comparison with `true`
As recommended by `statix check`.
* refactor: Avoid using deprecated `isNull`
As recommended by `statix check` and the documentation
<https://nixos.org/manual/nix/stable/language/builtins.html#builtins-isNull>.
* refactor: Simplify conditionals
As recommended by `statix check`.
* Update sources version
---------
Co-authored-by: Nicolas Mattia <nicolas@nmattia.com>
The `overrideCabal` mechanism, used to provide static executables, requires the `mkDerivation` argument in `callPackage` to be actually used. `foo/default.nix` currently ignores this argument, so this broke the static executable override.
The `callCabal2nix` invocation caused `cabal2nix` to be downloaded on
every install of `niv`. This introduces `foo`, a Nix function that does
exactly the same.