feat: ensure only unique images are returned

Signed-off-by: Bradley Jones <bradley.jones@anchore.com>

ecg/lib.go

@@ -151,7 +151,9 @@ func fetchImagesFromTasks(client *ecs.ECS, cluster string, tasks []*string) ([]i
 		return []inventory.ReportImage{}, err
 	}
 
-	images := []inventory.ReportImage{}
+	// build a map to ensure only unique images are returned
+	uniqueImages := make(map[string]inventory.ReportImage)
+
 	for r := range results.Tasks {
 		task := results.Tasks[r]
 		for c := range task.Containers {
@@ -160,12 +162,19 @@ func fetchImagesFromTasks(client *ecs.ECS, cluster string, tasks []*string) ([]i
 			if container.ImageDigest != nil {
 				digest = *container.ImageDigest
 			}
-			images = append(images, inventory.ReportImage{
+			uniqueName := fmt.Sprintf("%s@%s", *container.Image, digest)
+			uniqueImages[uniqueName] = inventory.ReportImage{
 				Tag:        *container.Image,
 				RepoDigest: digest,
-			})
+			}
 		}
 	}
 
+	// convert map of unique images to a slice
+	images := []inventory.ReportImage{}
+	for _, image := range uniqueImages {
+		images = append(images, image)
+	}
+
 	return images, nil
 }