Cherry pick the validateSourcePatterns. Correct exclusion patterns (.gradle and .idea are only at the root project level).

gradle/validation/validate-source-patterns.gradle

@@ -93,6 +93,7 @@ subprojects {
 configure(project(':lucene:benchmark')) {
   project.tasks.withType(ValidateSourcePatternsTask) {
     sourceFiles.exclude 'data/**'
+
     // Known .txt offenders.
     sourceFiles.exclude '**/reuters.first20.lines.txt', '**/trecQRels.txt'
   }
@@ -118,16 +119,23 @@ configure(rootProject) {
 
       // ourselves :-)
       exclude 'gradle/validation/validate-source-patterns.gradle'
+
+      // gradle and idea folders.
+      exclude '.gradle/**'
+      exclude '.idea/**'
     }
   }
 
   check.dependsOn validateSourcePatterns
 }
 
+@CacheableTask
 class ValidateSourcePatternsTask extends DefaultTask {
   private ProgressLoggerFactory progressLoggerFactory
 
   @InputFiles
+  @PathSensitive(PathSensitivity.RELATIVE)
+  @IgnoreEmptyDirectories
   FileTree sourceFiles
 
   @Inject