cargo fix: Print targets/features/cfg that will be fixed

[killercup]

With #5739, cargo fix learnt to check all targets by default. Since this might be a source of confusion, it would be helpful to also print out which targets we are fixing.

Running cargo fix should print out a line like this (right at the start):

Collecting suggestions for these targets: library, foo (binary), and bar (example). No optional features enabled. No specific cfg flags given.

[killercup]

This might require changing/dealing with some cargo internals. There is this method:

cargo/src/cargo/ops/cargo_compile.rs

Lines 440 to 448 in 6a7672e

	fn generate_targets<'a>(
	ws: &Workspace,
	profiles: &Profiles,
	packages: &[&'a Package],
	filter: &CompileFilter,
	default_arch_kind: Kind,
	resolve: &Resolve,
	build_config: &BuildConfig,
	) -> CargoResult<Vec<Unit<'a>>> {

as part of ops::compile, but it's not directly accessible in cargo-fix' entry function (here).

[JoshBrudnak]

@killercup I would like to help out with this. Thanks.

[killercup]

@JoshBrudnak this is assigned to me to remind me to check in on this. How's it going? :)

[JoshBrudnak]

I haven't had much time to work on it, but I'll be able to look into it later today. Thanks. 👍

[JoshBrudnak]

I guess I won't be working on this since @dwijnand took it. 😄

[dwijnand]

There's an initial, starting implementation in #5947, but @alexcrichton is hoping to get a few more user reports to figure out what needs printing. See his comment.

[dwijnand]

Move to close?

[alexcrichton]

Agreed yeah, we can always reopen if necessary!