feat: Preserve original tag when using digest strategy

pkg/argocd/argocd.go

@@ -522,6 +522,15 @@ func SetHelmImage(app *v1alpha1.Application, newImage *image.ContainerImage) err
 	return nil
 }
 
+// recordOriginalTag saves the original tag as an annotation (digest strategy only)
+func RecordOriginalTag(app *v1alpha1.Application, imageName, originalTag string) {
+    if app.Annotations == nil {
+        app.Annotations = make(map[string]string)
+    }
+    key := fmt.Sprintf("argocd-image-updater.argoproj.io/original-tag.%s", imageName)
+    app.Annotations[key] = originalTag
+}
+
 // GetKustomizeImage gets the image set in Application source matching new image
 // or an empty string if match is not found
 func GetKustomizeImage(app *v1alpha1.Application, newImage *image.ContainerImage) (string, error) {

pkg/argocd/argocd_test.go

@@ -1235,3 +1235,43 @@
 		assert.Equal(t, "baz", imgs[0].KustomizeImage.ImageName)
 	})
 }
+
+func Test_RecordOriginalTag(t *testing.T) {
+    tests := []struct {
+        name        string
+        app         *v1alpha1.Application
+        imageName   string
+        originalTag string
+    }{
+        {
+            name: "when annotations already exist",
+            app: &v1alpha1.Application{
+                ObjectMeta: metav1.ObjectMeta{
+                    Annotations: map[string]string{},
+                },
+            },
+            imageName:   "nginx",
+            originalTag: "1.14.2",
+        },
+        {
+            name: "when annotations is nil",
+            app: &v1alpha1.Application{
+                ObjectMeta: metav1.ObjectMeta{
+                    Annotations: nil,
+                },
+            },
+            imageName:   "redis",
+            originalTag: "6.0",
+        },
+    }
+
+    for _, tt := range tests {
+        t.Run(tt.name, func(t *testing.T) {
+            RecordOriginalTag(tt.app, tt.imageName, tt.originalTag)
+
+            key := fmt.Sprintf("argocd-image-updater.argoproj.io/original-tag.%s", tt.imageName)
+            require.NotNil(t, tt.app.Annotations)
+            require.Equal(t, tt.originalTag, tt.app.Annotations[key])
+        })
+    }
+}

pkg/argocd/update.go

@@ -288,6 +288,15 @@ func UpdateApplication(updateConf *UpdateConfiguration, state *SyncIterationStat
 		}
 
 		if needsUpdate(updateableImage, applicationImage, latest, vc.Strategy) {
+
+            if vc.Strategy == image.StrategyDigest && applicationImage.ImageTag != nil {
+                RecordOriginalTag(
+                    &updateConf.UpdateApp.Application,
+                    applicationImage.ImageName,
+                    applicationImage.ImageTag.TagName,
+                )
+            }
+
 			appImageWithTag := applicationImage.WithTag(latest)
 			appImageFullNameWithTag := appImageWithTag.GetFullNameWithTag()