ditto =
#(define-music-function (parser location mus) (ly:music?)
  #{
    #(set-accidental-style 'no-reset)
    $mus 
    #(set-accidental-style 'forget)
  #})

{
  #(set-accidental-style 'forget)
  cis' 
  \ditto cis' 
  cis'
  cis'
}