Twenty Twelve: 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, westonruter, joedolson.
See #10219.

git-svn-id: https://develop.svn.wordpress.org/trunk@61095 602fd350-edb4-49c9-b593-d223f7449a82

Author: joedolson

src/wp-content/themes/twentytwelve/functions.php

@@ -413,14 +413,28 @@ function wp_get_list_item_separator() {
 	function twentytwelve_content_nav( $html_id ) {
 		global $wp_query;
 
-		if ( $wp_query->max_num_pages > 1 ) : ?>
+		if ( $wp_query->max_num_pages > 1 ) :
+			$order   = get_query_var( 'order', 'DESC' );
+			$is_desc = ( 'DESC' === $order );
+
+			$new_posts_text = __( 'Newer posts <span class="meta-nav">&rarr;</span>', 'twentytwelve' );
+			$old_posts_text = __( '<span class="meta-nav">&larr;</span> Older posts', 'twentytwelve' );
+
+			$prev_link = $is_desc ? get_next_posts_link( $old_posts_text ) : get_previous_posts_link( $old_posts_text );
+			$next_link = $is_desc ? get_previous_posts_link( $new_posts_text ) : get_next_posts_link( $new_posts_text );
+			?>
 			<nav id="<?php echo esc_attr( $html_id ); ?>" class="navigation">
 				<h3 class="assistive-text"><?php _e( 'Post navigation', 'twentytwelve' ); ?></h3>
-				<div class="nav-previous"><?php next_posts_link( __( '<span class="meta-nav">&larr;</span> Older posts', 'twentytwelve' ) ); ?></div>
-				<div class="nav-next"><?php previous_posts_link( __( 'Newer posts <span class="meta-nav">&rarr;</span>', 'twentytwelve' ) ); ?></div>
+				<?php if ( $prev_link ) : ?>
+					<div class="nav-previous"><?php echo $prev_link; ?></div>
+				<?php endif; ?>
+
+				<?php if ( $next_link ) : ?>
+					<div class="nav-next"><?php echo $next_link; ?></div>
+				<?php endif; ?>
 			</nav><!-- .navigation -->
 			<?php
-	endif;
+		endif;
 	}
 endif;