directory.
From http://www.gnu.org/manual/tar/html_node/tar_123.html
REGTYPE
AREGTYPE
These flags represent a regular file. In order to be compatible with
older versions of tar, a typeflag value of AREGTYPE should be silently
recognized as a regular file. New archives should be created using
REGTYPE. Also, for backward compatibility, tar treats a regular file
whose name ends with a slash as a directory.