SpotlessTask: mark target as task input (#461)

* SpotlessTask: mark target as task input

* fix release notes for spotless-plugin-gradle

* remove release notes for plugin-gradle for validatePlugin warning fix

* SpotlessTask - mark target as internal

* fix formatting errors in validatePlugin-warning-fix

Author: rpalcolea

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

@@ -47,6 +47,7 @@
 import com.diffplug.spotless.LineEnding;
 import com.diffplug.spotless.PaddedCell;
 import com.diffplug.spotless.PaddedCellBulk;
+import com.diffplug.spotless.annotations.Internal;
 import com.diffplug.spotless.extra.integration.DiffMessageFormatter;
 
 public class SpotlessTask extends DefaultTask {
@@ -109,6 +110,7 @@ public FormatExceptionPolicy getExceptionPolicy() {
 
 	protected Iterable<File> target;
 
+	@Internal
 	public Iterable<File> getTarget() {
 		return target;
 	}