Comment 3 for bug 1644467

More comments about --unlink-first and --overwrite:
(Refer to http://www.linuxcommand.org/man_pages/tar1.html)
--unlink-first
remove existing files before extracting files of the same name

--overwrite
overwrite existing files and directory metadata when extracting

(Refer to http://lists.gnu.org/archive/html/bug-tar/2005-05/msg00056.html)
--overwrite: No matter what the file timestamp is, replace it with
             the archive version. Notice, that replacing means
             unlinking old file and creating a new one in its stead.
--unlink-first: Same as --overwrite, the only difference being that
                --unlink-first tries to unlink file before opening
                (even if it does not exist), while --overwrite
                unlinks it only after opening it returns EEXIST.