Provide --complete-copy Option for Instrumentation as in Istanbul

I used to run my instrumentation step with istanbul using something like this:

cross-env NODE_ENV=test istanbul instrument -i ./src/main/webapp/src -o ./src/main/webapp/instrumented --complete-copy

It basically instrumented all of the .js files, but also copied everything else, so that I could then build that folder and package it with my backend code (in this case a Java backend).

I'm trying to find a way to do it with nyc. When I run:

cross-env NODE_ENV=test nyc instrument ./src/main/webapp/src ./src/main/webapp/instrumented

That takes care of the files needing instrumentation, but I cannot get the --complete-copy behaviour present in istanbul.

I am currently doing the build with Webpack and babel-plugin-istanbul, which takes care of the problem for now, but it would be great if there was an equivalent using nyc instrument.