Find the storage path in shared folders first when connecting to Goog…

…le Drive

When connecting to Google Drive with a service account key, only files in the
service account's own hidden drive space are listable.  This change finds
the given storage path among shared folders first so that folders from the user
space can be made accessible via service account.

src/duplicacy_gcdstorage.go

@@ -256,6 +256,29 @@ func (storage *GCDStorage) listByName(threadIndex int, parentID string, name str
 	return file.Id, file.MimeType == GCDDirectoryMimeType, file.Size, nil
 }
 
+// Returns the id of the shared folder with the given name if it exists
+func (storage *GCDStorage) findSharedFolder(threadIndex int, name string) (string, error) {
+
+	query := "name = '" + name + "' and sharedWithMe and trashed = false and mimeType = 'application/vnd.google-apps.folder'"
+	q := storage.service.Files.List().Q(query).Fields("files(name, mimeType, id, size)").Spaces(storage.spaces)
+	if storage.driveID != GCDUserDrive {
+		q = q.DriveId(storage.driveID).IncludeItemsFromAllDrives(true).Corpora("drive").SupportsAllDrives(true)
+	}
+
+	fileList, err := q.Do()
+	if err != nil {
+		return "", err
+	}
+
+	if len(fileList.Files) == 0 {
+		return "", nil
+	}
+
+	file := fileList.Files[0]
+
+	return file.Id, nil
+}
+
 // getIDFromPath returns the id of the given path.  If 'createDirectories' is true, create the given path and all its
 // parent directories if they don't exist.  Note that if 'createDirectories' is false, it may return an empty 'fileID'
 // if the file doesn't exist.
@@ -427,9 +450,21 @@ func CreateGCDStorage(tokenFile string, driveID string, storagePath string, thre
 		storage.savePathID("", driveID)
 	}
 
-	storagePathID, err := storage.getIDFromPath(0, storagePath, true)
-	if err != nil {
-		return nil, err
+	storagePathID := ""
+
+	// When using service acount, check if storagePath is a shared folder which takes priority over regular folders.
+	if isServiceAccount && !strings.Contains(storagePath, "/") {
+		storagePathID, err = storage.findSharedFolder(0, storagePath)
+		if err != nil {
+			LOG_WARN("GCD_STORAGE", "Failed to check if %s is a shared folder: %v", storagePath, err)
+		}
+	}
+
+	if storagePathID == "" {
+		storagePathID, err = storage.getIDFromPath(0, storagePath, true)
+		if err != nil {
+			return nil, err
+		}
 	}
 
 	// Reset the id cache and start with 'storagePathID' as the root