Hi Mike, Thanks for reporting. Please note, that GNU tar manpage states, that it "is a short description of GNU tar" and suggests to use the GNU Tar Manual for detailed information "including examples and usage recommendations". Being such a "short description" explains why some details are omitted from it. On the other hand, the GNU Tar Manual contains, in section 6.4 says: "A cache directory tag is a short file with the well-known nameâ'CACHEDIR.TAG' and having a standard header specified in http://www.brynosaurus.com/cachedir/spec.html."; [1] This specification contains all details you noticed in your mail.
Regards, Sergey [1] https://www.gnu.org/software/tar/manual/html_node/exclude.html#index-exclude_002dcaches
