updated trackSourceFiles comments per #836 (comment)

Author: RBusarow

gradle-plugin/src/main/java/com/squareup/anvil/plugin/AnvilExtension.kt

@@ -94,7 +94,10 @@ public abstract class AnvilExtension @Inject constructor(
     .conventionFromProperty("com.squareup.anvil.addOptionalAnnotations", false)
 
   /**
-   * Track the source files for each generated file. This allows for two new behaviors:
+   * Enables incremental compilation support.
+   *
+   * This is achieved by maintaining a link between source files that exist before Anvil is run
+   * and the Anvil-generated files. This allows for two new behaviors:
    * - Generated code is "invalidated" and deleted when the source file is changed or deleted.
    * - Generated code is cached in a way that Gradle understands,
    *   and will be restored from cache along with other build artifacts.

gradle-plugin/src/main/java/com/squareup/anvil/plugin/VariantFilter.kt

@@ -43,6 +43,15 @@ public interface VariantFilter : Named {
    */
   public var addOptionalAnnotations: Boolean
 
+  /**
+   * Enables incremental compilation support.
+   *
+   * This is achieved by maintaining a link between source files that exist before Anvil is run
+   * and the Anvil-generated files. This allows for two new behaviors:
+   * - Generated code is "invalidated" and deleted when the source file is changed or deleted.
+   * - Generated code is cached in a way that Gradle understands,
+   *   and will be restored from cache along with other build artifacts.
+   */
   public var trackSourceFiles: Boolean
 }