org.el: New value for `org-todo-repeat-to-state'

* lisp/org.el (org-todo-repeat-to-state): Allow `t' to use
the previous TODO state.

* doc/org.texi (Repeated tasks): Document the new optional
value of `org-todo-repeat-to-state'.

doc/org.texi

@@ -6408,16 +6408,16 @@ Deadlines and scheduled items produce entries in the agenda when they are
 over-due, so it is important to be able to mark such an entry as completed
 once you have done so.  When you mark a DEADLINE or a SCHEDULE with the TODO
 keyword DONE, it will no longer produce entries in the agenda.  The problem
-with this is, however, that then also the @emph{next} instance of the
+with this is, however, is that then also the @emph{next} instance of the
 repeated entry will not be active.  Org mode deals with this in the following
-way: When you try to mark such an entry DONE (using @kbd{C-c C-t}), it will
-shift the base date of the repeating timestamp by the repeater interval, and
-immediately set the entry state back to TODO@footnote{In fact, the target
-state is taken from, in this sequence, the @code{REPEAT_TO_STATE} property or
-the variable @code{org-todo-repeat-to-state}.  If neither of these is
-specified, the target state defaults to the first state of the TODO state
-sequence.}.  In the example above, setting the state to DONE would actually
-switch the date like this:
+way: When you try to mark such an entry as DONE (using @kbd{C-c C-t}), it
+will shift the base date of the repeating timestamp by the repeater interval,
+and immediately set the entry state back to TODO@footnote{In fact, the target
+state is taken from, in this sequence, the @code{REPEAT_TO_STATE} property,
+the variable @code{org-todo-repeat-to-state} if it is a string, the previous
+TODO state if @code{org-todo-repeat-to-state} is @code{t} or the first state
+of the TODO state sequence.}.  In the example above, setting the state to
+DONE would actually switch the date like this:
 
 @example
 ** TODO Pay the rent

lisp/org.el

@@ -3026,13 +3026,17 @@ This option can also be set with on a per-file-basis with
 
 (defcustom org-todo-repeat-to-state nil
   "The TODO state to which a repeater should return the repeating task.
-By default this is the first task in a TODO sequence, or the previous state
-in a TODO_TYP set.  But you can specify another task here.
-alternatively, set the :REPEAT_TO_STATE: property of the entry."
+By default this is the first task of a TODO sequence or the
+previous state of a TYPE_TODO set.  But you can specify to use
+the previous state in a TODO sequence or a string.
+
+Alternatively, you can set the :REPEAT_TO_STATE: property of the
+entry, which has precedence over this option."
   :group 'org-todo
   :version "24.1"
-  :type '(choice (const :tag "Head of sequence" nil)
-		 (string :tag "Specific state")))
+  :type '(choice (const :tag "Use the previous TODO state" t)
+		 (const :tag "Use the head of the TODO sequence" nil)
+		 (string :tag "Use a specific TODO state")))
 
 (defcustom org-log-repeat 'time
   "Non-nil means record moving through the DONE state when triggering repeat.
@@ -12782,7 +12786,9 @@ This function is run automatically after each state change to a DONE state."
 	(when (and repeat (not (zerop (string-to-number (substring repeat 1)))))
 	  (when (eq org-log-repeat t) (setq org-log-repeat 'state))
 	  (let ((to-state (or (org-entry-get nil "REPEAT_TO_STATE" 'selective)
-			      org-todo-repeat-to-state)))
+			      (and (stringp org-todo-repeat-to-state)
+				   org-todo-repeat-to-state)
+			      (and org-todo-repeat-to-state org-last-state))))
 	    (org-todo (cond
 		       ((and to-state (member to-state org-todo-keywords-1))
 			to-state)