Some doc related to tab-stops

* doc/lispref/text.texi (Indent Tabs): Update related to tab-stops.

* lisp/indent.el (tab-stop-list): Doc fix.  Add :version.

doc/lispref/ChangeLog

+2014-01-28  Glenn Morris  <rgm@gnu.org>
+
+	* text.texi (Indent Tabs): Update related to tab-stops.
+
 2014-01-24  Glenn Morris  <rgm@gnu.org>
 
 	* control.texi (Handling Errors): Update with-demoted-errors.

doc/lispref/text.texi

@@ -2460,19 +2460,19 @@ stop feature only in a few major modes, such as Text mode.
 
 @deffn Command tab-to-tab-stop
 This command inserts spaces or tabs before point, up to the next tab
-stop column defined by @code{tab-stop-list}.  It searches the list for
-an element greater than the current column number, and uses that element
-as the column to indent to.  It does nothing if no such element is
-found.
+stop column defined by @code{tab-stop-list}.
 @end deffn
 
 @defopt tab-stop-list
-This variable is the list of tab stop columns used by
-@code{tab-to-tab-stops}.  The elements should be integers in increasing
-order.  The tab stop columns need not be evenly spaced.
-
-Use @kbd{M-x edit-tab-stops} to edit the location of tab stops
-interactively.
+This variable defines the tab stop columns used by @code{tab-to-tab-stop}.
+It should be either @code{nil}, or a list of increasing integers,
+which need not be evenly spaced.  The list is implicitly
+extended to infinity through repetition of the interval between the
+last and penultimate elements (or @code{tab-width} if the list has
+fewer than two elements).  A value of @code{nil} means a tab stop
+every @code{tab-width} columns.
+
+Use @kbd{M-x edit-tab-stops} to edit the location of tab stops interactively.
 @end defopt
 
 @node Motion by Indent

lisp/ChangeLog

 2014-01-28  Glenn Morris  <rgm@gnu.org>
 
+	* indent.el (tab-stop-list): Doc fix.  Add :version.
+
 	* vc/pcvs.el (vc-editable-p, vc-checkout): Remove unused declarations.
 	(cvs-append-to-ignore): Add compatibility alias.
 

lisp/indent.el

@@ -586,16 +586,17 @@ See also `indent-relative-maybe'."
 	  (move-marker opoint nil))
       (tab-to-tab-stop))))
 
-(defcustom tab-stop-list
-  nil
+(defcustom tab-stop-list nil
   "List of tab stop positions used by `tab-to-tab-stop'.
-This should be a list of integers, ordered from smallest to largest.
-It implicitly extends to infinity by repeating the last step (e.g. '(1 2 5)
-is equivalent to '(1 2 5 8 11)).
-If the list has less than 2 elements, `tab-width' is used as the \"last step\"."
+This should be nil, or a list of integers, ordered from smallest to largest.
+It implicitly extends to infinity through repetition of the last step.
+For example, '(1 2 5) is equivalent to '(1 2 5 8 11 ...).  If the list has
+fewer than 2 elements, `tab-width' is used as the \"last step\".
+A value of nil means a tab stop every `tab-width' columns."
   :group 'indent
+  :version "24.4"                       ; from explicit list to nil
+  :safe 'listp
   :type '(repeat integer))
-(put 'tab-stop-list 'safe-local-variable 'listp)
 
 (defvar edit-tab-stops-map
   (let ((map (make-sparse-keymap)))