Enable Gradle users to create steps that require a provisioner

Author: DavidGregory084

plugin-gradle/src/main/java/com/diffplug/gradle/spotless/FormatExtension.java

@@ -30,6 +30,7 @@
 import java.util.Random;
 import java.util.TreeMap;
 import java.util.function.Consumer;
+import java.util.function.Function;
 
 import javax.annotation.Nullable;
 import javax.inject.Inject;
@@ -300,6 +301,13 @@ public void addStep(FormatterStep newStep) {
 		steps.add(newStep);
 	}
 
+	/** Adds a new step that requires a Provisioner. */
+	public void addStep(Function<Provisioner, FormatterStep> createStepFn) {
+		requireNonNull(createStepFn);
+		FormatterStep newStep = createStepFn.apply(provisioner());
+		addStep(newStep);
+	}
+
 	/** Returns the index of the existing step with the given name, or -1 if no such step exists. */
 	protected int getExistingStepIdx(String stepName) {
 		for (int i = 0; i < steps.size(); ++i) {