"fatal: Not a valid object name develop" error when running brew upgrade/cleanup Whenever I run brew upgrade or brew cleanup I get this error in the output:

fatal: Not a valid object name develop


Although, it seems that upgrading works as expected. Where does the error come from and how to fix it?
It seems that the error has been caused by a misbehaving tap. After I've cleaned up taps with

brew untap &lt;tapname&gt;


the error disappeared.

P.S. to list all installed taps, just run:

brew tap