chistedit: change action for the correct item

We have an experimental config histedit.later-commits-first from c820866c52f9,
and when it's true, the order of commits in histedit UI is reversed, both in
text mode and in curses mode.

But before this patch key presses in curses mode would change histedit actions
in the same old order, i.e. trying to edit the latest commit (which would be
first now) would put "edit" action on the last commit in the list. This wasn't
a cosmetic issue, histedit would actually proceed to edit the first commit in
the list.

Let's map rules to display items (hopefully now correctly).

hgext/histedit.py

@@ -1581,14 +1581,16 b' pgup/K: move patch up, pgdn/J: move patc'
 
     def change_action(self, pos, action):
         """Change the action state on the given position to the new action"""
-        assert 0 <= pos < len(self.rules)
-        self.rules[pos].action = action
+        rule_pos = self.display_pos_to_rule_pos(pos)
+        assert 0 <= rule_pos < len(self.rules)
+        self.rules[rule_pos].action = action
 
     def cycle_action(self, pos, next=False):
         """Changes the action state the next or the previous action from
         the action list"""
-        assert 0 <= pos < len(self.rules)
-        current = self.rules[pos].action
+        rule_pos = self.display_pos_to_rule_pos(pos)
+        assert 0 <= rule_pos < len(self.rules)
+        current = self.rules[rule_pos].action
 
         assert current in KEY_LIST
 
@@ -1597,6 +1599,8 b' pgup/K: move patch up, pgdn/J: move patc'
             index += 1
         else:
             index -= 1
+        # using pos instead of rule_pos because change_action() also calls
+        # display_pos_to_rule_pos()
         self.change_action(pos, KEY_LIST[index % len(KEY_LIST)])
 
     def change_view(self, delta, unit):