Implement export to YAML

- add export commands for git sources and kustomizations
- add export e2e tests

cmd/tk/main.go

@@ -38,6 +38,9 @@ var rootCmd = &cobra.Command{
   # Trigger a git sync
   tk sync source git webapp-latest
 
+  # Export git sources in YAML format
+  tk export source git --all > sources.yaml
+
   # Create a kustomization for deploying a series of microservices
   tk create kustomization webapp-dev \
     --source=webapp-latest \
@@ -56,6 +59,9 @@ var rootCmd = &cobra.Command{
   # Suspend a kustomization reconciliation
   tk suspend kustomization webapp-dev
 
+  # Export kustomizations in YAML format
+  tk export kustomization --all > kustomizations.yaml
+
   # Resume a kustomization reconciliation
   tk resume kustomization webapp-dev