rexify --bundle recursively copies its payload on Darwin

The rex --bundle command executes cp -vR * rex.payload/. With GNU cp, it prevents copying directories into itself (tested on CentOS 6):

cp: cannot copy a directory, `rex.payload', into itself, `rex.payload/rex.payload'

With Darwin's cp command, it does not prevent this, so you get stuck in an infinite copy loop.

We could use rsync -av --exclude=rex.payload * rex.payload/ instead of using cp to fix this. Is there a better way?

Here is my setup:

$ uname -v
Darwin Kernel Version 15.0.0: Sat Sep 19 15:53:46 PDT 2015; root:xnu-3247.10.11~1/RELEASE_X86_64

$ rex -v
(R)?ex 1.3.3

Start at the rex --bundle command and reproduce the recursive-copy behavior on Darwin, comparing it with the documented GNU cp behavior. The work is done when bundling no longer copies rex.payload into itself or enters an infinite copy loop, while preserving the intended payload contents.