prow/config/jobs.go
func (ps Postsubmit) ShouldRun(baseRef string, changes ChangedFilesProvider) (bool, error) {
	if !ps.CouldRun(baseRef) {
		return false, nil
	}
	if determined, shouldRun, err := ps.RegexpChangeMatcher.ShouldRun(changes); err != nil {
		return false, err
	} else if determined {
		return shouldRun, nil
	}
	// Postsubmits default to always run
	return true, nil
}
func (ps Postsubmit) ShouldRun(baseRef string, changes ChangedFilesProvider) (bool, error) {
	if !ps.CouldRun(baseRef) {
		return false, nil
	}
	if determined, shouldRun, err := ps.RegexpChangeMatcher.ShouldRun(changes); err != nil {
		return false, err
	} else if determined {
		return shouldRun, nil
	}
	// Postsubmits default to always run
	return true, nil
}
// ShouldRun determines if the postsubmit should run in response to a
// set of changes. This is evaluated lazily, if necessary.