replace derivative crate with derive_more crate

[YJDoc2]

This PR carries over from #437 and changes the derivative crate to the derive_more crate. This is particularly for the Debug derives which were bandwhich's main usecase for derivative .

• Removed debug_fn (formatting fn) in code, as it only adds a fixed string, so directly used that string in the macro.
• Used Rust's normal Default derive, as our main use case for it was setting the default of Verbosity . But Verbosity itself is a simple struct having two u8 fields and a PhantomData , which also does a derive(Default) as the default for u8 is 0, the "normal" Default should be same as Verbosity::new(0, 0) .

[cyqsimon]

Thanks for the PR; code looks pretty good. Two comments:

1. Seems like derive_more requires 1.75.0. I'm okay with it, but we do need to bump MSRV in Cargo.toml.
2. Please add a changelog entry.

Then we're good to merge.

[YJDoc2]

Seems like derive_more requires 1.75.0. I'm okay with it, but we do need to bump MSRV in Cargo.toml.

Bumped rust-version in Cargo.toml

Please add a changelog entry.

I have added two entries, one for crate change and once for msrv bump, both pointing to this PR, is that ok? Should I combine them in just one entry?

Just a nit-pick: is this something your formatter did automatically? I think by default RA likes to order the imports in this order: std, foreign, crate.

Fixed, please check.

[cyqsimon]

I have added two entries, one for crate change and once for msrv bump, both pointing to this PR, is that ok? Should I combine them in just one entry?

Yeah either is fine really. Merging.