\version "2.19.37"
\language "deutsch"

\relative {
  \set Score.alternativeRestores = #'(measurePosition measureLength lastChord keyAlterations)
  \key d \minor
  \repeat volta 2 {
    d' e f g
    \key a \major
    a h cis d
  }
  \alternative {
    {
      e d cis h
      \key d \minor
      a g f e
    }
    {
      %\break
%%% VARIANT 1
      % do nothing, LilyPond’s default behaviour
%%% VARIANT 2
      %\once \set Staff.explicitKeySignatureVisibility = #end-of-line-invisible
      %\once \override Staff.KeyCancellation.break-visibility = #center-visible
%%% VARIANT 3
      %\once \set Staff.explicitKeySignatureVisibility = #begin-of-line-visible
      %\once \override Staff.KeyCancellation.break-visibility = #all-invisible
      e' fis gis e
    }
  }
  a1
}