-@value{op-incremental} is used in conjunction with @value{op-create},
-@value{op-extract} or @value{op-list} when backing up and restoring file
-systems. An archive cannot be extracted or listed with the
-@value{op-incremental} option specified unless it was created with the
-option specified. This option should only be used by a script, not by
-the user, and is usually disregarded in favor of
-@value{op-listed-incremental}, which is described below.
-
-@value{op-incremental} in conjunction with @value{op-create} causes
-@command{tar} to write, at the beginning of the archive, an entry for
-each of the directories that will be archived. The entry for a
-directory includes a list of all the files in the directory at the
-time the archive was created and a flag for each file indicating
-whether or not the file is going to be put in the archive.
-
-Note that this option causes @command{tar} to create a non-standard
-archive that may not be readable by non-@acronym{GNU} versions of the
-@command{tar} program.
-
-@value{op-incremental} in conjunction with @value{op-extract} causes
-@command{tar} to read the lists of directory contents previously stored
-in the archive, @emph{delete} files in the file system that did not
-exist in their directories when the archive was created, and then
-extract the files in the archive.
-
-This behavior is convenient when restoring a damaged file system from
-a succession of incremental backups: it restores the entire state of
-the file system to that which obtained when the backup was made. If
-@value{op-incremental} isn't specified, the file system will probably
-fill up with files that shouldn't exist any more.
-
-@value{op-incremental} in conjunction with @value{op-list} causes
-@command{tar} to print, for each directory in the archive, the list of
-files in that directory at the time the archive was created. This
-information is put out in a format that is not easy for humans to
-read, but which is unambiguous for a program: each file name is
-preceded by either a @samp{Y} if the file is present in the archive,
-an @samp{N} if the file is not included in the archive, or a @samp{D}
-if the file is a directory (and is included in the archive). Each
-file name is terminated by a null character. The last file is followed
-by an additional null and a newline to indicate the end of the data.
-
-@value{op-listed-incremental} acts like @value{op-incremental}, but when
-used in conjunction with @value{op-create} will also cause @command{tar}
-to use the file @var{snapshot-file}, which contains information about
-the state of the file system at the time of the last backup, to decide
-which files to include in the archive being created. That file will
-then be updated by @command{tar}. If the file @var{file} does not exist
-when this option is specified, @command{tar} will create it, and include
-all appropriate files in the archive.
-
-The file @var{file}, which is archive independent, contains the date
-it was last modified and a list of devices, inode numbers and
-directory names. @command{tar} will archive files with newer mod dates
-or inode change times, and directories with an unchanged inode number
-and device but a changed directory name. The file is updated after
-the files to be archived are determined, but before the new archive is
-actually created.