[Gradle] Document IncrementalSyncTask

^KT-58858 In Progress

libraries/tools/kotlin-gradle-plugin-api/src/common/kotlin/org/jetbrains/kotlin/gradle/tasks/IncrementalSyncTask.kt

@@ -7,7 +7,22 @@ import org.gradle.api.tasks.*
 import org.gradle.work.NormalizeLineEndings
 import java.io.File
 
+/**
+ * A task to incrementally synchronize a set of files between directories.
+ *
+ * Incremental synchronization support greatly reduces task execution time on subsequent builds when the set of files to be synchronized is large,
+ * but only a small amount have changed.
+ */
 interface IncrementalSyncTask : Task {
+
+    /**
+     * The collection of paths with files to copy.
+     *
+     * Should be configured using available methods in the [ConfigurableFileCollection]
+     * such as [ConfigurableFileCollection.from] or [ConfigurableFileCollection.setFrom].
+     *
+     * @see [ConfigurableFileCollection]
+     */
     @get:InputFiles
     @get:NormalizeLineEndings
     @get:IgnoreEmptyDirectories
@@ -15,9 +30,15 @@ interface IncrementalSyncTask : Task {
     @get:SkipWhenEmpty
     val from: ConfigurableFileCollection
 
+    /**
+     * The directory where the set of files are copied to.
+     */
     @get:OutputDirectory
     val destinationDirectory: Property<File>
 
+    /**
+     * @suppress
+     */
     @get:Internal
     @Deprecated("Use destinationDirProperty with Provider API", ReplaceWith("destinationDirProperty.get()"))
     val destinationDir: File