\version "2.19.44"

\relative g' {
  \set Score.barNumberVisibility = #all-bar-numbers-visible
  \override Score.BarNumber.break-visibility = #all-visible

  \time 4/2
  \set Staff.timeSignatureFraction = 2/2

  \repeat volta 2 {
    g2 r8  g8 [  bes8  c8 ]
    d2 c2 |
  }

  \alternative {
    {
      \partial 1
      d'4  d4.  bes8 a4 |
    }
    {
      \set Score.currentBarNumber = #4
      d4  d4.  bes8  a4
      g8 d'8 [  b8  c8 ]  d2 |
    }
  }

  \bar "|."
}