prow/plugins/trigger/generic-comment.go
func FilterPresubmits(honorOkToTest bool, gitHubClient GitHubClient, body string, pr *github.PullRequest, presubmits []config.Presubmit, logger *logrus.Entry) ([]config.Presubmit, []config.Presubmit, error) {
	org, repo, sha := pr.Base.Repo.Owner.Login, pr.Base.Repo.Name, pr.Head.SHA
	filter, err := presubmitFilter(honorOkToTest, gitHubClient, body, org, repo, sha, logger)
	if err != nil {
		return nil, nil, err
	}

	number, branch := pr.Number, pr.Base.Ref
	changes := config.NewGitHubDeferredChangedFilesProvider(gitHubClient, org, repo, number)
	toTrigger, toSkipSuperset, err := pjutil.FilterPresubmits(filter, changes, branch, presubmits, logger)
	if err != nil {
		return nil, nil, err
	}
	toSkip := determineSkippedPresubmits(toTrigger, toSkipSuperset, logger)
	return toTrigger, toSkip, err
}
func FilterPresubmits(honorOkToTest bool, gitHubClient GitHubClient, body string, pr *github.PullRequest, presubmits []config.Presubmit, logger *logrus.Entry) ([]config.Presubmit, []config.Presubmit, error) {
	org, repo, sha := pr.Base.Repo.Owner.Login, pr.Base.Repo.Name, pr.Head.SHA
	filter, err := presubmitFilter(honorOkToTest, gitHubClient, body, org, repo, sha, logger)
	if err != nil {
		return nil, nil, err
	}

	number, branch := pr.Number, pr.Base.Ref
	changes := config.NewGitHubDeferredChangedFilesProvider(gitHubClient, org, repo, number)
	toTrigger, toSkipSuperset, err := pjutil.FilterPresubmits(filter, changes, branch, presubmits, logger)
	if err != nil {
		return nil, nil, err
	}
	toSkip := determineSkippedPresubmits(toTrigger, toSkipSuperset, logger)
	return toTrigger, toSkip, err
}
// FilterPresubmits determines which presubmits should run. We only want to
// trigger jobs that should run, but the pool of jobs we filter to those that
// should run depends on the type of trigger we just got:
//  - if we get a /test foo, we only want to consider those jobs that match;
//    jobs will default to run unless we can determine they shouldn't
//  - if we got a /retest, we only want to consider those jobs that have
//    already run and posted failing contexts to the PR or those jobs that
//    have not yet run but would otherwise match /test all; jobs will default
//    to run unless we can determine they shouldn't
//  - if we got a /test all or an /ok-to-test, we want to consider any job
//    that doesn't explicitly require a human trigger comment; jobs will
//    default to not run unless we can determine that they should
// If a comment that we get matches more than one of the above patterns, we
// consider the set of matching presubmits the union of the results from the
// matching cases.