Don't call exist() on a directory when reading Annotated's metadata.

This might not work for "filesystems" that don't have a concept of a directory.
Instead, check for the existence of OBJECT files inside the directory.

Author: LTLA

package.json

@@ -1,6 +1,6 @@
 {
   "name": "jaspagate",
-  "version": "0.1.5",
+  "version": "0.1.6",
   "description": "Read and save objects in the takane format. This is a Javascript equivalent to the alabaster (R) and dolomite (Python) frameworks.",
   "author": {
     "name": "Aaron Lun",

src/globals.js

@@ -23,6 +23,8 @@ export class GlobalsInterface {
 
     /**
      * @param {string} path - Local path to a file, see {@linkcode GlobalsInterface#get get} for details.
+     * Note that this should not be a path to a directory;
+     * developers of {@linkcode readObject} functions should check for the existence of particular files inside a directory, rather than the directory itself.
      * @return {boolean|Promise<boolean>} Whether the `path` exists.
      */
     exists(path) {

src/metadata.js

@@ -1,7 +1,7 @@
 import { readObject, saveObject, readObjectFile } from "./general.js";
 
 export async function readAnnotatedMetadata(path, globals, options, optname) {
-    if (!(await globals.exists(path))) {
+    if (!(await globals.exists(path + "/OBJECT"))) { // check existence of file, not directory.
         return {};
     }