changing ottavation text after line break

[Immanuel Asmus]

Hello,

I’d like to have an OttavaBracket with ottavation "8", but after a line 
break, the ottavation should read "(8)". I cannot figure out whether 
this can be achieved with \alterBroken, since ottavation is not a 
feature of OttavaBracket. I read in the internals that the 
Ottava_spanner_engraver creates a text spanner, but TextSpanner is not 
the right grob for \alterBroken either.

I worked around my problem by adding

      \ottava #1
      \set Staff.ottavation = #"(8)"

where the line breaks. But maybe there is a universal solution for the 
whole score.

Regards,
Immanuel