Lily makedepend

[David A. Greene]

My project's getting big so I divided it into many .ly files and
started using make.

Now I'd like to have a makedepend-like tool to figure out which
.ly files are needed to produce what pdfs and help make know when
things need to be rebuilt.

Anyone have such a thing?  It shouldn't be hard to implement, but
was just wondering if it's been done already.

                             -Dave