Here's a utility I think would be useful.
Let's say I have a VHD with a single AVHD diff disk. In the VHD I've got two files: x.txt and y.txt in the AVHD I've got a new copy of x.txt.
I'd like a utility that would allow me to walk through the AVHD directory/file structure and tell me that x.txt is different than in the VHD.
This would allow us to create the beginnings of a differencing backup such that I could back up the x.txt from the AVHD file, modify the VHD (say by adding z.txt) and then recreate the AVHD with the updated x.txt.
It could even work by giving the new utility the filenames for the VHD and AVHD and outputing a new VHD containing only the directory/file structure that is ultimately changed along that AVHD line (in our example a VHD with the modified x.txt file and nothing
This would allow a process for modifying a base VHD such that attached AVHD files in a chain could be reconstructed safely after changing the base image.