feat: Add repeattitle

Author: codello

pdq-header.ily

@@ -13,8 +13,10 @@
 %!   title       - The title of the book (required).
 %!   subtitle    - The subtitle of the book (optional, but recommended).
 %!   subsubtitle - A subsubtitle of the book.
+%!   repeattitle - An optional variant of the title that will be used in the header of
+%!                 each page (if repeatTitle is true).
 %!   dedication  - A string containing a dedication of the work. This is displayed above
-%!                the (sub)titles.
+%!                 the (sub)titles.
 %!   instrument  - The name of the instrument the music is for.
 %!   publisher   - The publisher of a work.
 %!   version     - A string identifying the current version of a work.

pdq.ily

@@ -250,7 +250,8 @@ opt-default-tagline = #(get-option 'defaultTagline #f)
   headerCenter = \markup {
     \sans \unless \on-first-page \concat {
       \if-true #opt-repeat-title {
-        \fromproperty #'header:title
+        \fromproperty #'header:repeattitle
+        \when-not-property #'header:repeattitle \fromproperty #'header:title
         \when-property #'header:instrument " - "
       }
       \fromproperty #'header:instrument