The passes options causes Interscript to process files
more than once. This is sometimes necessary to get cross reference
information right. The default is currently 1.
Interscript may stop before running the specified number
of passes. It will do this if, and only if, every
buffered disk file ("named_file_sink") would write
an output the same as the existing file. In that case,
it assumes further passes wouldn't change anything, and stops.
This is called convergence.