#228 Undo Behavior after "Replace All"

[Elspeth Simpson White]

Currently, "Replace All" in the find and replace pane
finds all occurances of some text and replaces it with
something else in one action. However, if the user
then tries to undo the replace all, undo only undoes
one change at a time. A better behavior would be to
have undo undo everything that had been replaced at once.