The "descendants" command:

Usage: fossil descendants ?CHECKIN? ?OPTIONS?

Find all leaf descendants of the check-in specified or if the argument
is omitted, of the check-in currently checked out.

Options:
   -R|--repository FILE       Extract info from repository FILE
   -W|--width <num>           Width of lines (default is to auto-detect).
                              Must be >20 or 0 (= no limit, resulting in a
                              single line per entry).

See also: finfo, info, leaves