LilyPond: slightly improve lexing (#2283)

* Handle `--` and `__` as `Token.Punctuation` only if preceded by
  whitespace:

  ```
  <whitespace> --  ==>  hyphen (in lyrics mode)
  <whitespace> __  ==>  extender line (in lyrics mode)
  --               ==>  tenuto, neutral attachment (in music mode)
  __               ==>  portato, down attachment (in music mode)
  ```

* Handle `-` followed by a number as `Token.Number` only if preceded by
  whitespace.  This is purely heuristic, derived from the coding style shown
  in the LilyPond manuals.

  ```
  <whitespace> -3  ==>  integer (e.g., as a function argument)
  -3               ==>  fingering instruction
  ```

* Add forgotten `\maxima` note duration.

* Some legibility improvements by using verbose mode for regular
  expressions.

* Some comment additions and fixes.

* Update tests.

2 files changed, 18 insertions, 5 deletions

diff --git a/tests/examplefiles/lilypond/example.ly b/tests/examplefiles/lilypond/example.ly
index b2cbb81c..8a2eb1d6 100644
--- a/tests/examplefiles/lilypond/example.ly
+++ b/tests/examplefiles/lilypond/example.ly
@@ -76,7 +76,8 @@ piuPiano = \markup \italic "più piano"
     \key d \major
     \cadenzaOn
     deses'!4.~(\tweak thickness 4\( deses^\p-\signumcongruentiae_1\4
-    deses\longa) \myFunc { r } 4 des8 8[ <des ges>8]\)
+    deses\longa) \myFunc { r } 4
+      des8-- 8[__ \ottava -1 <des, ges>8]\) \ottava 0
     \bar "||"
     \cadenzaOff
     \pageBreak
@@ -100,7 +101,7 @@ piuPiano = \markup \italic "più piano"
   }
   \addlyrics {
     \set Score.melismaBusyProperties = #'()
-    My Lily -- Song
+    My Lily -- Song __
   }
   \chordmode {
     c cis:dim3+\dim des:maj7/+e\!
diff --git a/tests/examplefiles/lilypond/example.ly.output b/tests/examplefiles/lilypond/example.ly.output
index f5fbe531..b54953d4 100644
--- a/tests/examplefiles/lilypond/example.ly.output
+++ b/tests/examplefiles/lilypond/example.ly.output
@@ -399,21 +399,31 @@
 '}'           Punctuation
 ' '           Text.Whitespace
 '4'           Literal.Number
-' '           Text.Whitespace
+'\n      '    Text.Whitespace
 'des'         Pitch
 '8'           Literal.Number
+'--'          Name.Builtin.Articulation
 ' '           Text.Whitespace
 '8'           Literal.Number
 '['           Name.Builtin.Articulation
+'__'          Name.Builtin.Articulation
+' '           Text.Whitespace
+'\\ottava'    Name.Builtin.MusicFunction
+' '           Text.Whitespace
+'-1'          Literal.Number
 ' '           Text.Whitespace
 '<'           Punctuation
-'des'         Pitch
+'des,'        Pitch
 ' '           Text.Whitespace
 'ges'         Pitch
 '>'           Punctuation
 '8'           Literal.Number
 ']'           Name.Builtin.Articulation
 '\\)'         Name.Builtin.Articulation
+' '           Text.Whitespace
+'\\ottava'    Name.Builtin.MusicFunction
+' '           Text.Whitespace
+'0'           Literal.Number
 '\n    '      Text.Whitespace
 '\\bar'       Name.Builtin.MusicFunction
 ' '           Text.Whitespace
@@ -477,7 +487,7 @@
 'left'        Name.Builtin.GrobProperty
 '.'           Punctuation
 'padding'     Name.Builtin.GrobProperty
-'-5'          Literal.Number
+'-5'          Name.Builtin.Articulation
 '\\-'         Name.Builtin.Articulation
 '^"'          Literal.String
 'Some music'  Literal.String
@@ -573,6 +583,8 @@
 '--'          Punctuation
 ' '           Text.Whitespace
 'Song'        Text
+' '           Text.Whitespace
+'__'          Punctuation
 '\n  '        Text.Whitespace
 '}'           Punctuation
 '\n  '        Text.Whitespace