chore: import upstream snapshot with attribution

utils/slice.go

@@ -0,0 +1,54 @@
+package utils
+
+func Contains(slice []string, containsValue string) bool {
+	for _, sliceValue := range slice {
+		if sliceValue == containsValue {
+			return true
+		}
+	}
+
+	return false
+}
+
+func Unique(slice []string) []string {
+	keys := make(map[string]bool)
+	var list []string
+
+	for _, entry := range slice {
+		if _, value := keys[entry]; !value {
+			keys[entry] = true
+			list = append(list, entry)
+		}
+	}
+
+	return list
+}
+
+func EqualStringSlices(slice1 []string, slice2 []string) bool {
+	if len(slice1) != len(slice2) {
+		return false
+	}
+
+	for _, v := range slice1 {
+		if !Contains(slice2, v) {
+			return false
+		}
+	}
+
+	return true
+}
+
+// Diff returns the elements in `a` that aren't in `b`.
+func Diff(a, b []string) []string {
+	mb := make(map[string]struct{}, len(b))
+	for _, x := range b {
+		mb[x] = struct{}{}
+	}
+	var diff []string
+	for _, x := range a {
+		if _, found := mb[x]; !found {
+			diff = append(diff, x)
+		}
+	}
+	return diff
+}