drop ruby < 2.5 support

[ahorek]

this PR drops support for long EOL rubies as suggested by #213 (comment)

some gems still support very old versions, but I think Ruby 2.5 should be a reasonable minimum. This version is also currently tested by Github actions.

required_ruby_version = '>= 2.5.0'

it also applies rubocop autocorrect for Ruby 2.5 feature level (just styling)

[konsolebox]

Please consider having 2.0 as minimum instead. I'm proud of having my gems support 2.2 even though the version is already EOL. I don't want to change dependency parameters just because of this.

Also it doesn't make sense to include style alterations in same commit.

Lastly, isn't using =~ instead of match? good enough?

[kou]

it also applies rubocop autocorrect for Ruby 2.5 feature level (just styling)

Could you revert them? It adds many needles diffs.

Please consider having 2.0 as minimum instead. I'm proud of having my gems support 2.2 even though the version is already EOL. I don't want to change dependency parameters just because of this.

Could you explain why do you want to support Ruby 2.2?
For example, I maintain test-unit and it supports old Rubies as much as possible (including Ruby 2.1: https://github.com/test-unit/test-unit/blob/master/.github/workflows/test.yml ) to support migration from an old Ruby to a recent Ruby. Upgrading Ruby itself and testing framework at the same time is difficult. So I want to support "old Ruby + old testing framework" -> "old Ruby + new testing framework" -> "new Ruby + new testing framework" migration path.

[konsolebox]

Could you explain why do you want to support Ruby 2.2?

2.2 is simply the minimum version my gems needed. They were first released on that version and I simply didn't have any reason to upgrade.

2.2 if I recall right made significant ext-related changes that made me decide to start with it instead of 2.0 or 2.1.

I don't even have compatibility hacks in my code and my 2.2 tests still succeed.

[kou]

I see. Thanks.

[ahorek]

@kou I understand the maintenance burden, there're still people using it for ancient stuff... if it doesn't break we shouldn't touch it without a strong reason...

[kou]

I agree with you.
Note that we don't want to support EOL-ed Rubies actively for rake-compiler. If we need to create a shim for EOL-ed Rubies, we'll drop support for EOL-ed Rubies instead of creating a shim.