The "test-looks-like-utf" command:

Usage:  fossil test-looks-like-utf FILENAME

Options:
   -n|--limit <num> Repeat looks-like function <num> times, for
                    performance measurement. Default = 1;
   --utf8           Ignoring BOM and file size, force UTF-8 checking
   --utf16          Ignoring BOM and file size, force UTF-16 checking

FILENAME is the name of a file to check for textual content in the UTF-8
and/or UTF-16 encodings.