def retime_by_single_reference(have, want, reference)
      amount = want.references[reference][:timecode] -
               have.references[reference][:timecode]

      have.subtitles.each do |subtitle|
        subtitle[:start] += amount
        subtitle[:end] += amount
      end
    end
def retime_by_single_reference(have, want, reference)
      amount = want.references[reference][:timecode] -
               have.references[reference][:timecode]

      have.subtitles.each do |subtitle|
        subtitle[:start] += amount
        subtitle[:end] += amount
      end
    end
Applies a simple timeshift to the subtitle we {Have}.
 Each subtitle gets shifted forward/backward by the same amount of seconds.

 @param have [Have] the subtitles we {Have}
 @param want [Want] the subtitles we {Want}
 @param reference [Symbol, String] the key of the reference