Merge "jquery.tablesorter: Fix pre-JS selector to match wikitext-generated sortable...

diff --cc includes/skins/Skin.php
Simple merge

diff --cc resources/src/jquery.tablesorter.styles/jquery.tablesorter.styles.less
index 7ff7c11,589ae23..b926454
--- 1/resources/src/jquery.tablesorter.styles/jquery.tablesorter.styles.less
--- 2/resources/src/jquery.tablesorter.styles/jquery.tablesorter.styles.less
+++ b/resources/src/jquery.tablesorter.styles/jquery.tablesorter.styles.less
@@@ -1,10 -1,14 +1,16 @@@
  @import 'mediawiki.mixins';
  
 +/* stylelint-disable selector-class-pattern */
 +
  /* Table Sorting */
  
- .client-js .sortable:not( .jquery-tablesorter ) > thead > :last-of-type > th:not( .unsortable ),
+ // Reserve space for table sortable controls
+ // This selector is not perfect as it will not correctly handle cases with
+ // merged header cells, so ensure it is removed after the JS has run by using
+ // the :not( .jquery-tablesorter ) selector.
+ // It will still prevent a visible jump in the majority of simpler cases.
+ // The second selector in this rule is for after the JS has run.
+ .client-js .sortable:not( .jquery-tablesorter ) > * > tr:first-child > th:not( .unsortable ),
  .jquery-tablesorter th.headerSort {
        .background-image-svg( 'images/sort_both.svg', 'images/sort_both.png' );
        cursor: pointer;