viper: Undoing

 
 4.2.9 Undoing
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 ‘u U’
      Undo the latest change.
 ‘.’
      Repeat undo.
 ‘:q!’
      Quit Vi without writing.
 ‘:e!’
      Re-edit a messed-up file.
 ‘:rec’
      Recover file from autosave.  Viper also creates backup files that
      have a ‘~’ appended to them.