Incompatible lint doesnt trigger for included yaml

[FMorschel]

Steps:

1. Create new Dart project
2. Add very_good_analysis to dependencies (can be dev)
3. Swap the content of the analysis_option.yaml with:

include: package:very_good_analysis/analysis_options.7.0.0.yaml

linter:
  rules:
    prefer_relative_imports: true

If you look at https://pub.dev/packages/very_good_analysis they say they prefer the usage of always_use_package_imports. But this triggers nothing, only this way you'll have both lints triggering on a loop. I think we either should trigger incompatible_lint here or prefer the user manually written lint (prefered IMO).

CC @pq

[bwilkerson]

I think we should let users know when they have conflicting lints enabled, and shouldn't silently ignore what's enabled in included options files.

For example, if the included options file enables the lint in a newer version so that the conflict didn't exist until the version of the defining package was updated, then the user should have the opportunity to explicitly decide whether they want to continue to use their previous style or to conform to using the newly enabled style. They can't do that if we ignore the conflict.

[pq]

I'm in full agreement. If a lint you have registered locally conflicts with one you have included, I'd expect a warning.

Thanks for tracking this down, @FMorschel!