#5419 merge-differently-headed and merge-differently-dotted merge incorrectly with NoteColumn.force-hshift overridden

[Simon Albrecht]

Reported by Peter Terpstra:

\version "2.18.2" % same in 2.19.82

<<
  \mergeDifferentlyHeadedOn
  \mergeDifferentlyDottedOn
  {
    g'2 s
    g'8 % doesn’t happen with a quarter note, but with shorter values it does
  }
  \\
  {
    \override NoteColumn.force-hshift = #1
    g'2. s4
    g'2
  }
>>

[Malte Meyn]

What’s the expected or desired output here?

Should force-hshift move both voices? I don’t think so, it’s used for manual shifting of single voices.

Should the heads not be merged in this case? This would mean that the user relies on an automatism even if they change some things (force-hshift) manually. This seems contradictory to me. → no bug?