There are three main tasks here:

• spotless/plugin-gradle/src/main/java/com/diffplug/gradle/spotless/SpotlessTaskModern.java

  Line 40 in ca5f50d

  // TODO: implement using the InputChanges api

• spotless/plugin-gradle/src/main/java/com/diffplug/gradle/spotless/SpotlessExtensionModern.java

  Lines 47 to 48 in ca5f50d

  	// TODO level 1: implement SpotlessExtension::createFormatTasks, but using config avoidance
  	// TODO level 2: override configure(String name, Class<T> clazz, Action<T> configure) so that it is lazy

Each TODO can be implemented independently, and should probably be in a separate PR (the bottom two could maybe be in one PR). As detailed in #600, this code is tested by :plugin-gradle:modernTest, and is not yet being used by end-users, though it is possible to opt-in with -PspotlessModern=true.

PRs welcome!