anchor.diff:  ====
   
   // tag::undoredo[]
  -=== Undo previous command : `undo`
  +=== Undoing previous command : `undo`
   
   Restores the address book to the state before the previous _undoable_ command was executed. +
   Format: `undo`
  
positive.code: `undo` (reverses the `clear` command) +
  `undo` (reverses the `delete 1` command) +
  
  === Redo the previously undone command : `redo`
  
  Reverses the most recent `undo` command. +
  Format: `redo`
  
negative.code: * `edit 2 n/Betsy Crower t/` +
  Edits the name of the 2nd person to be `Betsy Crower` and clears all existing tags.
  
  === Locating persons by name: `find`
  
  Finds persons whose names contain any of the given keywords. +
  Format: `find KEYWORD [MORE_KEYWORDS]`
  