RFE: put all selection changes on the undo stack (even non-command)

[Elaine Meng]

Since there is a selection-changed trigger, maybe it would be possible to put all selection changes in the undo stack, including those from mouseclicks/drags and arrow-key actions. Otherwise there may be strange results if somebody undoes the last select-command change but there were intervening selection changes by other means.

[Conrad Huang]

Most selection changes, made via both command line and mouse, should now be undoable. However, "select down" may not work as expected after using undo because it depends on selection history, which undo does not track. Currently, undo leaves that history alone, which is probably wrong. Two possible choices are: (a) copy promotion history with every undo (expensive) or (b) clear promotion history on undo. Perhaps you can try it out (tomorrow) and see what you think.

[Conrad Huang]

After speaking with Elaine, we will keep the current behavior and document that "after undoing a selection, the down arrow and 'select down' command may not work as expected" because the arrow history and selection state are out of sync.