rules: add evaluationTimestamp when copy state. (#7775)

Signed-off-by: johncming <johncming@yahoo.com>

rules/manager.go

@@ -500,6 +500,7 @@ func nameAndLabels(rule Rule) string {
 // first is matched with the first, second with the second etc.
 func (g *Group) CopyState(from *Group) {
 	g.evaluationDuration = from.evaluationDuration
+	g.evaluationTimestamp = from.evaluationTimestamp
 
 	ruleMap := make(map[string][]int, len(from.rules))
 

rules/manager_test.go

@@ -657,6 +657,7 @@ func TestCopyState(t *testing.T) {
 	testutil.Equals(t, want, newGroup.seriesInPreviousEval)
 	testutil.Equals(t, oldGroup.rules[0], newGroup.rules[3])
 	testutil.Equals(t, oldGroup.evaluationDuration, newGroup.evaluationDuration)
+	testutil.Equals(t, oldGroup.evaluationTimestamp, newGroup.evaluationTimestamp)
 	testutil.Equals(t, []labels.Labels{{{Name: "l1", Value: "v3"}}}, newGroup.staleSeries)
 }