CopyDirectory copies the files under the source directory to dest directory.

CopyFile copies the file at source to dest Copied from vendor/github.com/mrunalp/fileutils/fileutils.go.

MkdirAllNewAs creates a directory (include any along the path) and then modifies ownership ONLY of newly created directories to the requested uid/gid.

TempDir wraps the ioutil.TempDir and add logic to handle private temp directories on OSX.