Unpacking a zip file from the source tree

Hello.

I have a zip file in the src directory of a project. I want to unpack
this zip file and insert the contents into the generated site directory
during the site phase.

What is the correct way to do this?

There's the "dependency:unpack" goal, but that only seems capable of
working with dependencies (which this zip file isn't). There's the
TrueZip plugin, but quite frankly, it seems defective (it silently
fails to do anything, and the documentation is no help at all).