Add fledgling unit tests to the file copying code in SUPlainInstallerInternals, and fix a couple small bugs in that code revealed as a process of writing the initial tests.
Significant refactoring of copyPathWithAuthentication... strip out stuff that is specific to Mac OS X 10.4 and earlier, and standardize on more modern (non-Carbon) file management methods, to avoid deprecation warnings on later OSes. Restructure the method so that the flow control is easier to follow.
Yikes! DO NOT work on /bin/ls and /bin/rm as the source files literally, because Sparkle's copy mechanism has behaviors that will attempt to modify the source file and will literally move it into the target destination, attempt to chmod, unquarantine, etc. We now copy the test tools from /bin/ into our temporary test folder.
Get rid of SUInstallerTempName, and all infrastrucure in methods, XPC, etc. designed to pass along this useless parameter that, ultimately in SUPlainInstallerInternals is never even used (it was not in use even before my recent refactoring).