status filters

CQL supports several filters to query the status of an ongoing or recently completed filter.

pathstartstart position
pathdebuginternal use only
pathlastpositiontail of last matching move of last matching path
pathcountnumber moves in path so far not including unfocused moves
pathcountunfocusedtotal moves so far including unfocused moves

The pathstart and pathlastposition filters, if invoked from outside any enclosing filter, have as value the start position or last position respectively of the most recent matching filter, if any.

Note: all these filters are experimental.