From aaf81e9bdcc6668112f3e55e851fd8524aaef578 Mon Sep 17 00:00:00 2001
From: Adrian Fernandez De La Torre <adri1197@gmail.com>
Date: Mon, 8 Sep 2025 16:10:06 +0200
Subject: [PATCH] Populate source-revision across all the resources at apply

Signed-off-by: Adrian Fernandez De La Torre <adri1197@gmail.com>
---
 .../controller/kustomization_controller.go    | 22 ++++++++++++++++++-
 internal/features/features.go                 |  7 ++++++
 main.go                                       |  7 ++++++
 3 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/internal/controller/kustomization_controller.go b/internal/controller/kustomization_controller.go
index 6ab99d7a..9e850c06 100644
--- a/internal/controller/kustomization_controller.go
+++ b/internal/controller/kustomization_controller.go
@@ -119,6 +119,7 @@ type KustomizationReconciler struct {
 	FailFast                   bool
 	GroupChangeLog             bool
 	StrictSubstitutions        bool
+	EnableRevisionAnnotation   bool
 }
 
 func (r *KustomizationReconciler) Reconcile(ctx context.Context, req ctrl.Request) (result ctrl.Result, retErr error) {
@@ -812,7 +813,26 @@ func (r *KustomizationReconciler) apply(ctx context.Context,
 		return false, nil, err
 	}
 
-	if cmeta := obj.Spec.CommonMetadata; cmeta != nil {
+	var revisionAnnotations map[string]string
+	if r.EnableRevisionAnnotation {
+		if obj.Status.LastAppliedRevision == "" || revision != obj.Status.LastAppliedRevision {
+			revisionAnnotations = map[string]string{
+				fmt.Sprintf("%s/source-revision", eventv1.Group): revision,
+			}
+		}
+		if originRevision != "" && originRevision != obj.Status.LastAppliedOriginRevision {
+			revisionAnnotations[fmt.Sprintf("%s/source-revision", eventv1.Group)] = originRevision
+		}
+	}
+
+	cmeta := obj.Spec.CommonMetadata
+	if cmeta != nil {
+		if cmeta.Annotations == nil {
+			cmeta.Annotations = make(map[string]string)
+		}
+		for k, v := range revisionAnnotations {
+			cmeta.Annotations[k] = v
+		}
 		ssautil.SetCommonMetadata(objects, cmeta.Labels, cmeta.Annotations)
 	}
 
diff --git a/internal/features/features.go b/internal/features/features.go
index 2053384b..feb174e0 100644
--- a/internal/features/features.go
+++ b/internal/features/features.go
@@ -59,6 +59,10 @@ const (
 
 	// ExternalArtifact controls whether the ExternalArtifact source type is enabled.
 	ExternalArtifact = "ExternalArtifact"
+
+	// EnableRevisionAnnotation controls whether source revision annotations
+	// should be enabled on applied resources.
+	EnableRevisionAnnotation = "EnableRevisionAnnotation"
 )
 
 var features = map[string]bool{
@@ -83,6 +87,9 @@ var features = map[string]bool{
 	// ExternalArtifact
 	// opt-in from v1.7
 	ExternalArtifact: false,
+	// EnableRevisionAnnotation
+	// opt-in from v1.8
+	EnableRevisionAnnotation: true,
 }
 
 func init() {
diff --git a/main.go b/main.go
index a26bb80d..179452a7 100644
--- a/main.go
+++ b/main.go
@@ -293,6 +293,12 @@ func main() {
 		os.Exit(1)
 	}
 
+	enableRevisionAnnotation, err := features.Enabled(features.EnableRevisionAnnotation)
+	if err != nil {
+		setupLog.Error(err, "unable to check feature gate "+features.EnableRevisionAnnotation)
+		os.Exit(1)
+	}
+
 	var tokenCache *pkgcache.TokenCache
 	if tokenCacheOptions.MaxSize > 0 {
 		var err error
@@ -330,6 +336,7 @@ func main() {
 		StatusManager:              fmt.Sprintf("gotk-%s", controllerName),
 		StrictSubstitutions:        strictSubstitutions,
 		TokenCache:                 tokenCache,
+		EnableRevisionAnnotation:   enableRevisionAnnotation,
 	}).SetupWithManager(ctx, mgr, controller.KustomizationReconcilerOptions{
 		RateLimiter:            runtimeCtrl.GetRateLimiter(rateLimiterOptions),
 		WatchConfigsPredicate:  watchConfigsPredicate,