glog.go
func (l *Log) SetVFilepath(spec FilepathSpec) {
	l.mu.Lock()
	defer l.mu.Unlock()
	l.setVState(l.verbosity, nil, spec.filter, true)
}
func (l *Log) SetVFilepath(spec FilepathSpec) {
	l.mu.Lock()
	defer l.mu.Unlock()
	l.setVState(l.verbosity, nil, spec.filter, true)
}
// SetModuleSpec sets the comma-separated list of pattern=N settings for
// file-filtered logging