#4740 Wrong beam subdivision when duration == baseMoment

[Urs Liska]

Beam subdivision behaves wrongly when the duration of a stem equals baseMoment.

The following example features two cases, one real-world example with mixed durations and one beam with regular notes.

\version "2.18.2"

\relative f' {
  \set subdivideBeams = ##t
  \set baseMoment = #(ly:make-moment 1/16)
  g16 [ c ~ c64 b a g fis g a g ]

  \set baseMoment = #(ly:make-moment 1/32)
  g32 g g g g g g g
}

Expected behaviour:

First beam: The first two stems (16) should be connected with two beams, followed by a subdivision with one beam (during the tied note).

Second beam: sequence of 3-2-3-1-3-2-3 beams, exactly as if baseMoment was set to 1/16.

Actual behaviour with four versions:

First beam: Identically wrong with any version since 2.18.2.

Second beam:

• 2.18.2: Beamlet plus one beam (wrong)
• 2.19.20 (4355 applied): complicatedly wrong
• 2.19.34 (Commit 0382ed88 applied): Simplified and technically correct (but not desired) output)
• 2.19.35 (4704 applied): Same as with 2.19.20

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I will consider this in the context of 4738