make sure parent handler affects child until sethandler is called on …

…child

log15_test.go

@@ -363,3 +363,16 @@ func TestIndependentSetHandler(t *testing.T) {
 		t.Fatalf("parent handler affected by child")
 	}
 }
+
+// https://github.com/inconshreveable/log15/issues/16
+func TestInheritHandler(t *testing.T) {
+	t.Parallel()
+
+	parent, _, r := testLogger()
+	child := parent.New()
+	parent.SetHandler(DiscardHandler())
+	child.Info("test")
+	if r.Msg == "test" {
+		t.Fatalf("child handler affected not affected by parent")
+	}
+}

logger.go

@@ -94,9 +94,7 @@ func (l *logger) write(msg string, lvl Lvl, ctx []interface{}) {
 }
 
 func (l *logger) New(ctx ...interface{}) Logger {
-	// copy the child's handler
-	h := *l.h
-	return &logger{append(l.ctx, normalize(ctx)...), &h}
+	return &logger{append(l.ctx, normalize(ctx)...), &swapHandler{handler: l.h}}
 }
 
 func (l *logger) Debug(msg string, ctx ...interface{}) {