fix(ci): Inconsistent use of IMAGE_REGISTRY and IMAGE_NAMESPACE Makefile variables (#25846) (#25860)

Signed-off-by: Eugene Doudine <eugene.doudine@octopus.com>

hack/update-manifests.sh

@@ -12,14 +12,39 @@ KUSTOMIZE=kustomize
 
 cd "${SRCROOT}/manifests/ha/base/redis-ha" && ./generate.sh
 
-# Image repository configuration - can be overridden in forks
-IMAGE_REGISTRY="${IMAGE_REGISTRY:-quay.io}"
-IMAGE_NAMESPACE="${IMAGE_NAMESPACE:-argoproj}"
-IMAGE_REPOSITORY="${IMAGE_REPOSITORY:-argocd}"
+# Empty defaults - to avoid errors for unset env. variables
+IMAGE_REGISTRY="${IMAGE_REGISTRY:-}"
+IMAGE_NAMESPACE="${IMAGE_NAMESPACE:-}"
 IMAGE_TAG="${IMAGE_TAG:-}"
+# Image repository configuration - can be overridden in forks
+IMAGE_REPOSITORY="${IMAGE_REPOSITORY:-argocd}"
+
+# Apply defaults if needed
+if [[ -n $IMAGE_REGISTRY ]];then
+    if [[ -z $IMAGE_NAMESPACE ]]; then
+	echo "IMAGE_NAMESPACE must be set when IMAGE_REGISTRY is set (e.g. IMAGE_NAMESPACE=argoproj)" >&2
+	exit 1
+    fi
+    # both registry and namespace set, nothing to do
+else  # registry not set
+    if [[ -z $IMAGE_NAMESPACE ]]; then
+	# Neither namespace nor registry given - apply the default values
+	IMAGE_REGISTRY="${IMAGE_REGISTRY:-quay.io}"
+	IMAGE_NAMESPACE="${IMAGE_NAMESPACE:-argoproj}"
+    fi
+    # If namespace is set, then it's an image without registry or
+    # registry is given as part of namespace (old convention)
+fi
 
 # Construct full image name
-FULL_IMAGE_NAME="${IMAGE_REGISTRY}/${IMAGE_NAMESPACE}/${IMAGE_REPOSITORY}"
+# Note: keeping same logic as in Makefile for docker images
+FULL_IMAGE_NAME="${IMAGE_REPOSITORY}"
+if [[ -n $IMAGE_NAMESPACE ]]; then
+    FULL_IMAGE_NAME="${IMAGE_NAMESPACE}/${FULL_IMAGE_NAME}"
+fi
+if [[ -n $IMAGE_REGISTRY ]]; then
+    FULL_IMAGE_NAME="${IMAGE_REGISTRY}/${FULL_IMAGE_NAME}"
+fi
 
 # Auto-detect current image in manifests for release workflows
 detect_current_image() {