BadPort is returned when a port number is outside the valid range (1..65535).

MissingAnnex is returned when a repository doesn't have annex initialised (can also be used as a warning).

MissingGitUser is returned when a string is assumed to be a git configuration but does not contain a user (missing @).

MissingURLScheme is returned when a string is assumed to be a URL but does not contain a scheme (missing ://).

NotInRepo is returned when a command needs to be run from within a repository.

RequiresLogin is returned when a command requires the user to be logged in.