src/admin/class-papi-admin-entry-post.php
public function get_revision_ui_diff( $return, $compare_from, $compare_to ) {
		$meta = get_post_meta( $compare_from->ID );
		$meta = is_array( $meta ) ? $meta : [];

		foreach ( $meta as $key => $value ) {
			if ( $key[0] === '_' && $key !== papi_get_page_type_key() ) {
				continue;
			}

			$content_from = papi_data_get( $compare_from->ID, $key );
			$content_to = papi_data_get( $compare_to->ID, $key );

			$diff = wp_text_diff( $content_from, $content_to, [
				'show_split_view' => true
			] );

			if ( $diff ) {
				$return[] = [
					'id'   => $key,
					'name' => $key,
					'diff' => $diff,
				];
			}
		}

		return $return;
	}
public function get_revision_ui_diff( $return, $compare_from, $compare_to ) {
		$meta = get_post_meta( $compare_from->ID );
		$meta = is_array( $meta ) ? $meta : [];

		foreach ( $meta as $key => $value ) {
			if ( $key[0] === '_' && $key !== papi_get_page_type_key() ) {
				continue;
			}

			$content_from = papi_data_get( $compare_from->ID, $key );
			$content_to = papi_data_get( $compare_to->ID, $key );

			$diff = wp_text_diff( $content_from, $content_to, [
				'show_split_view' => true
			] );

			if ( $diff ) {
				$return[] = [
					'id'   => $key,
					'name' => $key,
					'diff' => $diff,
				];
			}
		}

		return $return;
	}
Filters the fields displayed in the post revision diff UI.

@param  array   $return
@param  WP_Post $compare_from
@param  WP_Post $compare_to

@return array