\version "2.19.55"

\pointAndClickOff

one   = { a'4\p 4 4 4 2\<   2   4\mp 4 4 4 \repeat volta 2 { 4 4 4 4 } }
two   = { d'4\p 4 4 4 2\<   2   4\mp 4 4 4 \repeat volta 2 { 4 4 4 4 } }
three = { d'4\p 4 4 4 4\< 4 4 4 4\mp 4 4 4 \repeat volta 2 { 4 4 4 4 } }
four  = { a'4\p 4 4 4 2\<   2   4\mp 4 4 4 \repeat volta 2 { 4 4 4 4 } 1 4 4 4 4}
five  = { d'4\p 4 4 4 4\< 4 4 4 4\mp 4 4 4 \repeat volta 2 { 4 4 4 4 } 1 4 4 4 4}

\markup { "\partcombine works as expected"}

\score {
    \new Staff \partcombine \one \two
    \layout{ }
}

\markup { "Bug 1: \< \mp should be merged as above"}

\score {
    \new Staff \partcombine \one \three
    \layout{ }
}

\markup { "Bug 2a: \unfoldRepeats \partcombine forgets to engrave repeat of 2nd voice at end of music"}

\score {
    \unfoldRepeats { 
        \new ChoirStaff <<
             \new Staff { \one \bar "|." }
             \new Staff { \three \bar "|." }
             \new Staff { \partcombine \one \three \bar "|." }
         >>
    }
    \layout{ }
}

\markup { "Bug 2b: Adding music seems to fix bug 2a, but we see that now some music at the end is missing."}

\score {
    \unfoldRepeats { 
        \new ChoirStaff <<
             \new Staff { \four \bar "|." }
             \new Staff { \five \bar "|." }
             \new Staff { \partcombine \four \five \bar "|." }
         >>
    }
    \layout{ }
}