When the JsonRestClient.publish(...) method is called with a true value for "versionable", the JsonRestClient method creates a FileNode object that only sets the 'jcr:mixinTypes' property to 'mix:versionable' _on the "jcr:content" child node. It needs to instead make the 'nt:file' node versionable instead, and have the "jcr:content" child node be versioned via the (default) OPV value of COPY.

Basically, lines 117-119 need to move after line 103.