cli: don't ask for password if repository is not connected (#627)

cli/config.go

@@ -47,8 +47,12 @@ func onCtrlC(f func()) {
 }
 
 func openRepository(ctx context.Context, opts *repo.Options, required bool) (repo.Repository, error) {
-	if _, err := os.Stat(repositoryConfigFileName()); os.IsNotExist(err) && !required {
-		return nil, nil
+	if _, err := os.Stat(repositoryConfigFileName()); os.IsNotExist(err) {
+		if !required {
+			return nil, nil
+		}
+
+		return nil, errors.Errorf("repository is not connected. See https://kopia.io/docs/repositories/")
 	}
 
 	maybePrintUpdateNotification(ctx)