Allow workspaceContains to specify directories (fixes #8295).

src/vs/base/node/pfs.ts

@@ -193,6 +193,13 @@ export function fileExistsWithResult<T>(path: string, successResult: T): TPromis
 	});
 }
 
+export function existsWithResult<T>(path: string, successResult: T): TPromise<T> {
+	return exists(path).then((exists) => {
+		return exists ? successResult : null;
+	}, (err) => {
+		return TPromise.wrapError(err);
+	});
+}
 
 function removeNull<T>(arr: T[]): T[] {
 	return arr.filter(item => (item !== null));

src/vs/workbench/node/extensionHostMain.ts

@@ -246,7 +246,7 @@ export class ExtensionHostMain {
 
 		return TPromise.join(
 			Object.keys(desiredFilesMap).map(
-				(fileName) => pfs.fileExistsWithResult(paths.join(folderPath, fileName), fileName)
+				(fileName) => pfs.existsWithResult(paths.join(folderPath, fileName), fileName)
 			)
 		).then((fileNames: string[]) => {
 			fileNames.forEach((existingFileName) => {