User should be able to specify username and/or password from CLI.

[Zodiase]

Currently I assume the user would only use one account, thus saving it in the preference file is good enough to prevent repetitively entering passwords.
However, I do see that some people may want to use a different account at some point. This is very difficult to do right now if the user has already signed in with an account. There is no way to sign out unless the user manually deletes the preference file, which is not a good option for normal users.

The proposed solution is to update the CLI options with this addition:

bart [-u|--username <username> [--password <password>]]

When the username option is provided, the current user info in the preference file is ignored, and the tool will not prompt for a username.
When the password option is provided along with the username, the tool will not prompt for a password.

To discourage passing password in a plain text way like this, the password option doesn't have a shorthand.

If login is successful, the provided username-password pair will replace the existing user info in the preferences.