Recognise individual items in List resource

It's not enough to be able to update images in a List resource, we
must be able to recognise them in the first place.

The YAML parser makes this a little tricky, because it doesn't give
you access to the bytes (like `UnmarshalJSON` does), so if we want
typed resources, we have to parse them generically and marshal them
back out to bytes. (Another way to do it would be to unmarshal into a
baseObject, then into the specific object based on the kind. That
might be a good refactoring.)

cluster/kubernetes/resource/load.go

@@ -71,7 +71,15 @@ func ParseMultidoc(multidoc []byte, source string) (map[string]resource.Resource
 		if obj == nil {
 			continue
 		}
-		objs[obj.ResourceID().String()] = obj
+		// Lists must be treated specially, since it's the
+		// contained resources we are after.
+		if list, ok := obj.(*List); ok {
+			for _, item := range list.Items {
+				objs[item.ResourceID().String()] = item
+			}
+		} else {
+			objs[obj.ResourceID().String()] = obj
+		}
 	}
 
 	if err := chunks.Err(); err != nil {

cluster/kubernetes/resource/load_test.go

@@ -5,6 +5,7 @@ import (
 	"reflect"
 	"testing"
 
+	"github.com/weaveworks/flux"
 	"github.com/weaveworks/flux/cluster/kubernetes/testfiles"
 	"github.com/weaveworks/flux/resource"
 )
@@ -117,6 +118,39 @@ data:
 	}
 }
 
+func TestUnmarshalList(t *testing.T) {
+	doc := `---
+kind: List
+metadata:
+  name: list
+items:
+- kind: Deployment
+  metadata:
+    name: foo
+- kind: Service
+  metadata:
+    name: bar
+`
+	res, err := unmarshalObject("", []byte(doc))
+	if err != nil {
+		t.Fatal(err)
+	}
+	list, ok := res.(*List)
+	if !ok {
+		t.Fatal("did not parse as a list")
+	}
+	if len(list.Items) != 2 {
+		t.Fatalf("expected two items, got %+v", list.Items)
+	}
+	for i, id := range []flux.ResourceID{
+		flux.MustParseResourceID("default:deployment/foo"),
+		flux.MustParseResourceID("default:service/bar")} {
+		if list.Items[i].ResourceID() != id {
+			t.Errorf("At %d, expected %q, got %q", i, id, list.Items[i].ResourceID())
+		}
+	}
+}
+
 func debyte(r resource.Resource) resource.Resource {
 	if res, ok := r.(interface {
 		debyte()

cluster/kubernetes/resource/resource.go

@@ -110,6 +110,12 @@ func unmarshalKind(base baseObject, bytes []byte) (resource.Resource, error) {
 			return nil, err
 		}
 		return &ss, nil
+	case "List":
+		var list = List{baseObject: base}
+		if err := yaml.Unmarshal(bytes, &list); err != nil {
+			return nil, err
+		}
+		return &list, nil
 	case "":
 		// If there is an empty resource (due to eg an introduced comment),
 		// we are returning nil for the resource and nil for an error