Centralise adapter types

Since the generic commands tend to share a few of the methods they
need -- at least AsClientObject -- it's worth having just one wrapper
struct for each API type, and adding methods to it where necessary.

For the automation types, I put these in auto.go.

While doing this I also did some tidying:

 - I changed the name of the wrappers to `<type>Adapter`, and the
   generic adapter to `universalAdapter` (it's only needed for delete,
   so far).

 - I de-exported and renamed some interface methods e.g.,
   `exportItem`. They aren't needed outside the package.

Signed-off-by: Michael Bridgen <michael@weave.works>

cmd/flux/auto.go

@@ -0,0 +1,99 @@
+/*
+Copyright 2020 The Flux authors
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package main
+
+import (
+	"k8s.io/apimachinery/pkg/runtime"
+
+	autov1 "github.com/fluxcd/image-automation-controller/api/v1alpha1"
+	imagev1 "github.com/fluxcd/image-reflector-controller/api/v1alpha1"
+)
+
+// These are general-purpose adapters for attaching methods to, for
+// the various commands. The *List adapters implement len(), since
+// it's used in at least a couple of commands.
+
+// imagev1.ImageRepository
+type imageRepositoryAdapter struct {
+	*imagev1.ImageRepository
+}
+
+func (a imageRepositoryAdapter) asRuntimeObject() runtime.Object {
+	return a.ImageRepository
+}
+
+// imagev1.ImageRepositoryList
+
+type imageRepositoryListAdapter struct {
+	*imagev1.ImageRepositoryList
+}
+
+func (a imageRepositoryListAdapter) asRuntimeObject() runtime.Object {
+	return a.ImageRepositoryList
+}
+
+func (a imageRepositoryListAdapter) len() int {
+	return len(a.ImageRepositoryList.Items)
+}
+
+// imagev1.ImagePolicy
+
+type imagePolicyAdapter struct {
+	*imagev1.ImagePolicy
+}
+
+func (a imagePolicyAdapter) asRuntimeObject() runtime.Object {
+	return a.ImagePolicy
+}
+
+// imagev1.ImagePolicyList
+
+type imagePolicyListAdapter struct {
+	*imagev1.ImagePolicyList
+}
+
+func (a imagePolicyListAdapter) asRuntimeObject() runtime.Object {
+	return a.ImagePolicyList
+}
+
+func (a imagePolicyListAdapter) len() int {
+	return len(a.ImagePolicyList.Items)
+}
+
+// autov1.ImageUpdateAutomation
+
+type imageUpdateAutomationAdapter struct {
+	*autov1.ImageUpdateAutomation
+}
+
+func (a imageUpdateAutomationAdapter) asRuntimeObject() runtime.Object {
+	return a.ImageUpdateAutomation
+}
+
+// autov1.ImageUpdateAutomationList
+
+type imageUpdateAutomationListAdapter struct {
+	*autov1.ImageUpdateAutomationList
+}
+
+func (a imageUpdateAutomationListAdapter) asRuntimeObject() runtime.Object {
+	return a.ImageUpdateAutomationList
+}
+
+func (a imageUpdateAutomationListAdapter) len() int {
+	return len(a.ImageUpdateAutomationList.Items)
+}