with user or group
mappings.  Empty lines are ignored.  Comments are introduced with
# sign (unless quoted) and extend to the end of the corresponding
line.  Each non-empty line defines translation for a single UID (GID).
It must consist of two fields, delimited by any amount of whitespace:

     OLDNAME NEWNAME[:NEWID]

OLDNAME is either a valid user (group) name or a ID prefixed with +.  Unless
NEWID is supplied, NEWNAME must also be either a valid name or a
+ID.  Otherwise, both NEWNAME and NEWID need not be listed in the
system user database.

* New option --clamp-mtime

The new --clamp-mtime option changes the behavior of --mtime to only
use the time specified if the file mtime is newer than the given time.
The --clamp-mtime option can only be used together with	--mtime.

Typical use case is to make builds reproducible: to loose less
information, it's better to keep the original date of an archive,
except for files modified during the build process. In that case, using
reference (and thus reproducible) timestamps for the latter is good
enough.

See <https://wiki.debian.org/ReproducibleBuilds> for more information.

* Deprecated --preserve option removed

* Sparse file detection

Tar now uses SEEK_DATA/SEEK_HOLE on systems that support it.  This
allows for considerable speed-up in sparse-file detection.

New option --hole-detection is provided, that allows the user to
select the algorithm used for hole detection.  Available arguments
are:

  --hole-detection=seek
     Use lseek(2) SEEK_DATA and SEEK_HOLE "whence" parameters.

  --hole-detection=raw
     Scan entire file before storing it to determine where holes
     are located.

The default is to use "seek" whenever possible, and fall back to
"raw" otherwise.

