prow/github/fakegithub/fakegithub.go
func (f *FakeClient) AddLabel(owner, repo string, number int, label string) error {
	labelString := fmt.Sprintf("%s/%s#%d:%s", owner, repo, number, label)
	if sets.NewString(f.IssueLabelsAdded...).Has(labelString) {
		return fmt.Errorf("cannot add %v to %s/%s/#%d", label, owner, repo, number)
	}
	if f.RepoLabelsExisting == nil {
		f.IssueLabelsAdded = append(f.IssueLabelsAdded, labelString)
		return nil
	}
	for _, l := range f.RepoLabelsExisting {
		if label == l {
			f.IssueLabelsAdded = append(f.IssueLabelsAdded, labelString)
			return nil
		}
	}
	return fmt.Errorf("cannot add %v to %s/%s/#%d", label, owner, repo, number)
}
func (f *FakeClient) AddLabel(owner, repo string, number int, label string) error {
	labelString := fmt.Sprintf("%s/%s#%d:%s", owner, repo, number, label)
	if sets.NewString(f.IssueLabelsAdded...).Has(labelString) {
		return fmt.Errorf("cannot add %v to %s/%s/#%d", label, owner, repo, number)
	}
	if f.RepoLabelsExisting == nil {
		f.IssueLabelsAdded = append(f.IssueLabelsAdded, labelString)
		return nil
	}
	for _, l := range f.RepoLabelsExisting {
		if label == l {
			f.IssueLabelsAdded = append(f.IssueLabelsAdded, labelString)
			return nil
		}
	}
	return fmt.Errorf("cannot add %v to %s/%s/#%d", label, owner, repo, number)
}
// AddLabel adds a label