Single slur with two endings (well, kind of) for repeats

[Alberto Simões]

Hi

Suppose something like

\repeat volta 2 {
   c4 c4(
}
\alternative {
  {c4) r}
  {c2) }   %%% this
}

the second end slur is not typeset.
is there any elegant way to draw it, or i should try to make an 
invisible note somewhere?

Thanks
Alberto