PR comment fixes

- Add comment to explain sql driver update behaviour when it comes to updating custom labels
- Apply custom labels in memory driver

Signed-off-by: Evans Mungai <mbuevans@gmail.com>

internal/storage/driver/records.go

@@ -114,6 +114,10 @@ func newRecord(key string, rls *rspb.Release) *record {
 	var lbs labels
 
 	lbs.init()
+
+	// apply custom labels
+	lbs.fromMap(rls.Labels)
+
 	lbs.set("name", rls.Name)
 	lbs.set("owner", "helm")
 	lbs.set("status", rls.Info.Status.String())

internal/storage/driver/sql.go

@@ -576,6 +576,20 @@ func (s *SQL) Create(key string, rel release.Releaser) error {
 }
 
 // Update updates a release.
+//
+// Custom labels on an existing revision are meant to be preserved. A release's
+// labels are set by Create, and a revision keeps the labels it was created with
+// once it is superseded, rather than picking up the labels of the upgrade that
+// superseded it. TestUpgradeRelease_Labels in pkg/action is what asserts this.
+//
+// The drivers arrive at that from opposite directions. Here labels live in a
+// separate table written only by Create, so an update leaves them untouched. The
+// configmaps, memory and secrets drivers instead store labels on the record
+// itself and replace the record wholesale on update, so they have to re-apply
+// the labels every time or the update would discard all of them. A side effect
+// is that those drivers persist a label change where this driver silently would
+// not. No caller changes labels between Create and Update, so the two agree in
+// practice.
 func (s *SQL) Update(key string, rel release.Releaser) error {
 	rls, err := releaserToV1Release(rel)
 	if err != nil {

pkg/storage/driver/records.go

@@ -114,6 +114,10 @@ func newRecord(key string, rls *rspb.Release) *record {
 	var lbs labels
 
 	lbs.init()
+
+	// apply custom labels
+	lbs.fromMap(rls.Labels)
+
 	lbs.set("name", rls.Name)
 	lbs.set("owner", "helm")
 	lbs.set("status", rls.Info.Status.String())

pkg/storage/driver/sql.go

@@ -576,6 +576,20 @@ func (s *SQL) Create(key string, rel release.Releaser) error {
 }
 
 // Update updates a release.
+//
+// Custom labels on an existing revision are meant to be preserved. A release's
+// labels are set by Create, and a revision keeps the labels it was created with
+// once it is superseded, rather than picking up the labels of the upgrade that
+// superseded it. TestUpgradeRelease_Labels in pkg/action is what asserts this.
+//
+// The drivers arrive at that from opposite directions. Here labels live in a
+// separate table written only by Create, so an update leaves them untouched. The
+// configmaps, memory and secrets drivers instead store labels on the record
+// itself and replace the record wholesale on update, so they have to re-apply
+// the labels every time or the update would discard all of them. A side effect
+// is that those drivers persist a label change where this driver silently would
+// not. No caller changes labels between Create and Update, so the two agree in
+// practice.
 func (s *SQL) Update(key string, rel release.Releaser) error {
 	rls, err := releaserToV1Release(rel)
 	if err != nil {