845f0ca15e
If some of the branches have no tags at all (like in the case of feature branches or early master branches), the listing of branches in list-changes fails. This problem was introduced in I4f06d6cfaa8ea332d9326ccd8a5e69c749589529 since we switched to subprocess' check_output instead of call. Change-Id: Id8c61662ecf3a9424c3b4e21fb36f0ed8c01d6b1