I guess that pointing to a dedicated git-sha is not a very good option. What do you think?
You mean pointing to a git revision within the published version of PropCheck? I don't know if this is something that is frowned upon.. How about this: We point to PropEr's git revision, but only release a RC candidate. With that, the update of PropCheck should not automatically propagate to users, unless they explicitly switch to the RC version.
maybe_improper_list()and so on either.