\mbinput is broken [Was: Re: nested lilypond-book files?]

[Oscar A. Valdez]

\include and \input are the standard LaTeX procedures to split a long
document into several .tex files. lilypond-book requires that the
commands be used as \mbinclude and \mbinput with Lilypond .ly files.

\mbinclude works as expected, and, like plain \include, does a
\clearpage before and after the included file. \mbinput, however, is
broken. lilypond-book crashes with the following output:

Traceback (most recent call last):
  File "/usr/bin/lilypond-book", line 1540, in ?
    do_file(input_filename)
  File "/usr/bin/lilypond-book", line 1424, in do_file
    chunks = read_doc_file(input_filename)
  File "/usr/bin/lilypond-book", line 1007, in read_doc_file
    chunks = chop_chunks(chunks, 'input', do_input_file, 1)
  File "/usr/bin/lilypond-book", line 953, in chop_chunks
    newchunks = newchunks + func(m)
  File "/usr/bin/lilypond-book", line 880, in do_input_file
    return read_doc_file(m.group('filename'))
IndexError: no such group

Is this a known bug, or is there something wrong with my installation? I
need to use \mbinput, because I don't want the \clearpages inserted by
\mbinclude.

Oscar A. Valdez