It seems that using diskpart merge to merge a differencing drive and parent does not provide an option to target a new VHD file. Fine, I've backed up my parent vhd files, and the child.
When I execute the merge will the parents remain unmodified, or will they have the content of the child merged in them.
I need the child VHD to be standalone, but the other child vhd to continue to work off the parent.
What bit of documentation I have been able to find, is not clear as which direction the data flows.