deb-new-reprepro-repository should likely run reprepro export at the end

[mih]

This would give an immediately usable (still empty) repository. In case a distribution builder needs access to a custom archive to pull in additional packages dependencies that this very machinery had put into that archive, running reprepro export at the beginning of the process, would enable configuraing the builder what that APT source right from the start.

The downside is that any archive dataset would starts with a bunch of useless keys.

An alternative would be to add this info to the command documentation.