bug#23789: Emacs 25.0.94: Patch to make sort-lines respect visible lines (fairly urgent)

[Robert Weiner]

sort-lines calls forward-line rather than forward-visible line, so if
you have emacs outline entries that are collapsed/hidden to single lines
each and you try to sort them, their bodies and subtrees are sorted
separately because forward-visible-line is not used.

This patch fixes this problem and also unifies the calling convention of
forward-visible-line with that of forward-line (allowing it to take an
optional argument) leading to a cleaner calling convention.

Please apply it as soon as you can as Hyperbole uses sort-lines to sort
its contact manager records and right now this doesn't work.  Although,
sort-subr could be called directly for this application, sort-lines
should work properly with both visible and invisible text and the patch
is quite simple.

Thanks,

Bob
--------

In GNU Emacs 25.0.94.1 (x86_64-apple-darwin13.4.0, NS appkit-1265.21 Version 10.9.5 (Build 13F1603))
 of 2016-05-17 built on builder10-9.local
Windowing system distributor 'Apple', version 10.3.1404
Configured using:
 'configure --with-ns '--enable-locallisppath=/Library/Application
 Support/Emacs/${version}/site-lisp:/Library/Application
 Support/Emacs/site-lisp''

Configured features:
NOTIFY ACL LIBXML2 ZLIB TOOLKIT_SCROLL_BARS NS

Important settings:
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix

----------------

*** sort-orig.el.gz 2016-06-18 11:31:13.000000000 -0400
--- sort.el.gz 2016-06-18 11:31:13.000000000 -0400
***************
*** 210,216 ****
        (goto-char (point-min))
        (let ;; To make `end-of-line' and etc. to ignore fields.
   ((inhibit-field-text-motion t))
! (sort-subr reverse 'forward-line 'end-of-line)))))
 
  ;;;###autoload
  (defun sort-paragraphs (reverse beg end)
--- 210,216 ----
        (goto-char (point-min))
        (let ;; To make `end-of-line' and etc. to ignore fields.
   ((inhibit-field-text-motion t))
! (sort-subr reverse 'forward-visible-line 'end-of-visible-line)))))
 
  ;;;###autoload
  (defun sort-paragraphs (reverse beg end)


*** simple-orig.el.gz 2016-06-18 11:29:58.000000000 -0400
--- simple.el.gz 2016-06-18 11:29:58.000000000 -0400
***************
*** 4909,4918 ****
  (kill-region (point)
       (progn (forward-visible-line arg) (point))))))
 
! (defun forward-visible-line (arg)
!   "Move forward by ARG lines, ignoring currently invisible newlines only.
  If ARG is negative, move backward -ARG lines.
  If ARG is zero, move to the beginning of the current line."
    (condition-case nil
        (if (> arg 0)
   (progn
--- 4909,4919 ----
  (kill-region (point)
       (progn (forward-visible-line arg) (point))))))
 
! (defun forward-visible-line (&optional arg)
!   "Move forward by optional ARG lines (default = 1), ignoring currently invisible newlines only.
  If ARG is negative, move backward -ARG lines.
  If ARG is zero, move to the beginning of the current line."
+   (if (null arg) (setq arg 1))
    (condition-case nil
        (if (> arg 0)
   (progn