bug#16744: 24.3.50; REGRESSION: C-h v does not show doc for `ediff-highlight-all-diffs'

[Eli Zaretskii]

> Date: Thu, 13 Feb 2014 11:31:58 -0800 (PST)
> From: Drew Adams <drew.adams@oracle.com>
> 
> emacs -Q
> M-x load-library ediff
> C-h v ediff-highlight-all-diffs
> 
> No doc shown, just an empty "Documentation:".

That's because of the ediff-defvar-local macro:

  (defcustom ediff-highlight-all-diffs t
    "If nil, only the selected differences are highlighted.
  Otherwise, all difference regions are highlighted, but the selected region is
  shown in brighter colors."
    :type 'boolean
    :group 'ediff-highlighting)
  (ediff-defvar-local ediff-highlight-all-diffs t "")

It is invoked (here and elsewhere) with an empty string as the doc, so
that's what you get.

Michael, what's the purpose here?