kubernetes/staging/src/k8s.io/apimachinery/pkg/apis/meta/v1/labels.go

// Clones the given selector and returns a new selector with the given key and value added.
// Returns the given selector, if labelKey is empty.
func CloneSelectorAndAddLabel(selector *LabelSelector, labelKey, labelValue string) *LabelSelector { … }

// AddLabelToSelector returns a selector with the given key and value added to the given selector's MatchLabels.
func AddLabelToSelector(selector *LabelSelector, labelKey, labelValue string) *LabelSelector { … }

// SelectorHasLabel checks if the given selector contains the given label key in its MatchLabels
func SelectorHasLabel(selector *LabelSelector, labelKey string) bool { … }