I replaced issue-15518-1.patch. I believe it now addresses all the concerns expressed thus far. If reviewed favorably, I will extend it to clean-up the pre-existing tests to address the concerns noted about them, especially since the filecmpdata directory added by this patch contains the information necessary to test the rest of the filecmp module rather than resorting to creating temp directories and files. It seems less than ideal to me to have the test script use a mixed model for accessing test data (both temp and filecmpdata directories). But that's not my call.