[O] [PATCH] Fix alphabetic sorting for headlines, tags

[Sebastian Reuße]

* org.el (org-sort-entries): Use collated sorting.
(org-tags-sort-function): Use collated sorting.
(org-string-collate-greaterp): Add helper-function to use as defcustom
option, since there is no ‘string-collate-greaterp’ in Emacs.

‘org-sort-entries’ and ‘org-tags-sort-function’ advertise alphabetic
sorting, but actually sort based only on character code.  This
produces non-alphabetic orderings of strings in non-ASCII locales.

E. g., German Umlauts “Ä Ü Ö” are alphabetically sorted as if they
were “A U O”, whereas sorting based on character-code will place them
after “Z”, which is unexpected.
---
 lisp/org.el | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/lisp/org.el b/lisp/org.el
index 688e48bcc..dc0611b87 100644
--- a/lisp/org.el
+++ b/lisp/org.el
@@ -3558,8 +3558,8 @@ (defcustom org-tags-sort-function nil
   :group 'org-tags
   :type '(choice
          (const :tag "No sorting" nil)
-         (const :tag "Alphabetical" string<)
-         (const :tag "Reverse alphabetical" string>)
+         (const :tag "Alphabetical" string-collate-lessp)
+         (const :tag "Reverse alphabetical" org-string-collate-greaterp)
          (function :tag "Custom function" nil)))
 
 (defvar org-tags-history nil
@@ -8803,7 +8803,7 @@ (defun org-sort-entries
             (t (error "Invalid sorting type `%c'" sorting-type))))
          nil
          (cond
-          ((= dcst ?a) 'string<)
+          ((= dcst ?a) 'string-collate-lessp)
           ((= dcst ?f)
            (or compare-func
                (and interactive?
@@ -8913,6 +8913,12 @@ (defun org-context-p (&rest contexts)
                    (org-in-item-p)))
       (goto-char pos))))
 
+(defun org-string-collate-greaterp (s1 s2 &optional locale ignore-case)
+  "Return t if S1 is greater than S2 in collation order.
+
+LOCALE and IGNORE-CASE are handled as in `string-collate-lessp'."
+  (not (string-collate-lessp s1 s2 locale ignore-case)))
+
 ;;;###autoload
 (defun org-run-like-in-org-mode (cmd)
   "Run a command, pretending that the current buffer is in Org mode.
-- 
2.16.1