I have added (in my git tree) this to the error message: dgit: archive query failed (queried because --since-version not specified)
and this to the part of the manpage that discusses `dgit build': dgit's build operations access the the network, to get the -v option right. See -v, below. I decided it would be too intrusive to replicate that text for dgit sbuild, dgit gbp-build, and so on. I hope that is satisfactory. Thanks, Ian.