redding/dassets — pull request #58 by kellyredding (2013-08-07 21:25:59+00:00)
Title: have a `NullSourceFile` 'proxy' the digest path if is a combination

The effect of this change is "recursive combinations". This allows
you to specify combination digest paths in the source paths of
another combination.

Closes #50.

@jcredding ready for review.