I found that Wix v3 uses a tool (heat.exe) to "harvest" information into WiX fragments. Either I am looking in the wrong location, or this is thinly documented.
What is the best way to auto-generate a WiX fragment (likely using heat.exe) for a complex folder structure that contains media files:
such that they can be built into an installer via WiX and would withstand upgrades and patches with decorum?
It was (fairly) pointed out that v3 is not yet "done" (thus the scarceness of documentation and tutorials). The sense that I get now is that it is non-trivial to automate this in my build scripts, and the tools are growing right now to ease this.
In my experience John Robbins' Paraffin solves alot of the issues with tallow.exe (heat.exe in v3). I'm not sure if Paraffin plays nicely with v3, but it might be worth checking out.
FYI, I've used Paraffin in a build process and it allowed me to remove the previous 2-3 step cleanup process that involved a powershell script.