support leafOnly option

src/vs/workbench/services/decorations/browser/decorations.ts

@@ -20,6 +20,7 @@ export interface IResourceDecoration {
 	readonly suffix?: string;
 	readonly color?: ColorIdentifier;
 	readonly icon?: URI | { dark: URI, light: URI };
+	readonly leafOnly?: boolean;
 }
 
 export interface IDecorationsProvider {

src/vs/workbench/services/decorations/browser/decorationsService.ts

@@ -89,7 +89,7 @@ class DecorationProviderWrapper {
 			const childTree = this._data.findSuperstr(key);
 			if (childTree) {
 				childTree.forEach(([, value]) => {
-					if (value && !isThenable<void>(value)) {
+					if (value && !isThenable<void>(value) && !value.leafOnly) {
 						callback(value);
 					}
 				});