Twenty Nineteen: Fix post navigation to respect sort order.

Change the labels on post navigation links when the sort order is changed so the labels accurately reflect the target entries.

Previously, if the sort order was reversed, 'Older' or 'Previous' links would navigate to newer entries and 'Newer' or 'Next' links would navigate to older entries.

Props jikamens, dancameron, obenland, shrey0shrivastava, sirlouen, sabernhardt, shailu25, joedolson.
See #10219.

git-svn-id: https://develop.svn.wordpress.org/trunk@61093 602fd350-edb4-49c9-b593-d223f7449a82

Author: joedolson

src/wp-content/themes/twentynineteen/inc/template-tags.php

@@ -221,17 +221,20 @@ function twentynineteen_comment_form( $order ) {
 	 * Displays the next and previous posts navigation.
 	 */
 	function twentynineteen_the_posts_navigation() {
+		$order          = get_query_var( 'order', 'DESC' );
+		$new_posts_text = __( 'Newer posts', 'twentynineteen' );
+		$old_posts_text = __( 'Older posts', 'twentynineteen' );
 		the_posts_pagination(
 			array(
 				'mid_size'  => 2,
 				'prev_text' => sprintf(
 					'%s <span class="nav-prev-text">%s</span>',
 					twentynineteen_get_icon_svg( 'chevron_left', 22 ),
-					__( 'Newer posts', 'twentynineteen' )
+					( 'DESC' === $order ) ? $new_posts_text : $old_posts_text
 				),
 				'next_text' => sprintf(
 					'<span class="nav-next-text">%s</span> %s',
-					__( 'Older posts', 'twentynineteen' ),
+					( 'DESC' === $order ) ? $old_posts_text : $new_posts_text,
 					twentynineteen_get_icon_svg( 'chevron_right', 22 )
 				),
 			)