Some repositories used to create older deliverables have since been
retired. Add support for a flag to designate them as such, and refactor
the flag test code to make it a little cleaner and to define tags
clearly in one place
Change-Id: I7002f2a13409edfbd76e681b267e28bc28e1a53e
Signed-off-by: Doug Hellmann <doug@doughellmann.com>