Trivial Description
When using FileUtils.copyDirectory to copy directories with subdirectories, the source will overwrite all files that exist in the destination directory, but not the subdirectories themselves. The files inside the subdirectories will be overwritten. The only difference that I've noticed thus far is that this preserves the old file dates of the subdirectories rather than using the dates from the source or the current date, if preserveFileDate is set to 'false.'