diff --git a/wp-admin/includes/revision.php b/wp-admin/includes/revision.php
index 2b3102f27d..ea714394ad 100644
--- a/wp-admin/includes/revision.php
+++ b/wp-admin/includes/revision.php
@@ -55,7 +55,22 @@ function wp_get_revision_ui_diff( $post, $compare_from, $compare_to ) {
 	$return = array();
 
 	foreach ( _wp_post_revision_fields() as $field => $name ) {
+		/**
+		 * Contextually filter a post revision field.
+		 *
+		 * The dynamic portion of the hook name, $field, corresponds to each of the post
+		 * fields of the revision object being iterated over in a foreach statement.
+		 *
+		 * @since 3.6.0
+		 *
+		 * @param string  $compare_from->$field The current revision field to compare to or from.
+		 * @param string  $field                The current revision field.
+		 * @param WP_Post $compare_from         The revision post object to compare to or from.
+		 * @param string  null                  The context of whether the current revision is the old or the new one. Values are 'to' or 'from'.
+		 */
 		$content_from = $compare_from ? apply_filters( "_wp_post_revision_field_$field", $compare_from->$field, $field, $compare_from, 'from' ) : '';
+
+		//duplicate_hook
 		$content_to = apply_filters( "_wp_post_revision_field_$field", $compare_to->$field, $field, $compare_to, 'to' );
 
 		$diff = wp_text_diff( $content_from, $content_to, array( 'show_split_view' => true ) );