I read about dhall’s imports, and I don’t think I like it. If I add a text configuration mechanism to software, I do not want it accessing the network by default, full stop. To me, a “safe” configuration language means that parsing terminates, does not have side effects, does not touch the network, and that parsing the same file twice gives the same output unless I explicitly change an input. Pulling a prelude off of github does misses several of these requirements.
(Having your config file fail to parse if your network is down is bad, bad news if that config is needed to bring your network up. It’s also bad news if a parsing failure due to a transient network issue leaves your system in a state where it won’t quickly recover if the network comes back.)