Issue 4687/1: Let \etc in partial markup commands stand for any argum…

…ents

Previously, \etc could only stand for a final markup argument.  Now an
arbitrary kind and number of arguments from the last markup command in
a markup command chain may be omitted.

Example:

quarter-markup = \markup \note-by-number #2 \etc

\markup { 3/8: \quarter #1 #UP }

lily/parser.yy

@@ -3671,7 +3671,7 @@ full_markup:
 	;
 
 partial_markup:
-	markup_mode markup_head_1_list ETC
+	markup_mode markup_partial_function ETC
 	{
 		$$ = MAKE_SYNTAX (partial_markup, @2, $2);
 		parser->lexer_->pop_state ();
@@ -3789,6 +3789,37 @@ markup_command_list_arguments:
 	}
 	;
 
+markup_partial_function:
+	MARKUP_FUNCTION markup_arglist_partial
+	{
+		$$ = scm_list_1 (scm_cons ($1, scm_reverse_x ($2, SCM_EOL)));
+	}
+	| markup_head_1_list MARKUP_FUNCTION markup_arglist_partial
+	{
+		$$ = scm_cons (scm_cons ($2, scm_reverse_x ($3, SCM_EOL)),
+			       $1);
+	}
+	;
+
+markup_arglist_partial:
+	EXPECT_MARKUP markup_arglist_partial
+	{
+		$$ = $2;
+	}
+	| EXPECT_SCM markup_arglist_partial
+	{
+		$$= $2;
+	}
+	| EXPECT_MARKUP markup_command_list_arguments
+	{
+		$$ = $2;
+	}
+	| EXPECT_SCM markup_command_list_arguments
+	{
+		$$ = $2;
+	}
+	;
+
 markup_head_1_item:
 	MARKUP_FUNCTION EXPECT_MARKUP markup_command_list_arguments {
 	  $$ = scm_cons ($1, scm_reverse_x ($3, SCM_EOL));

scm/ly-syntax-constructors.scm

@@ -203,14 +203,17 @@ into a @code{MultiMeasureTextEvent}."
 (define-public (partial-markup commands)
   ;; Like composed-markup-list, except that the result is a single
   ;; markup command that can be applied to one markup
-  (define (compose arg)
+  (define (compose rest)
     (fold
      (lambda (cmd prev) (append cmd (list prev)))
-     arg
-     commands))
-  (let ((chain (lambda (layout props arg)
-                 (interpret-markup layout props (compose arg)))))
-    (set-object-property! chain 'markup-signature (list markup?))
+     (append (car commands) rest)
+     (cdr commands)))
+  (let ((chain (lambda (layout props . rest)
+                 (interpret-markup layout props (compose rest)))))
+    (set! (markup-command-signature chain)
+          (list-tail
+           (markup-command-signature (caar commands))
+           (length (cdar commands))))
     chain))
 
 (define-public (property-set context property value)