I'm trying to slowly clean this up a bit, and moving functionality out
into the folder types and having those methods not reach into model is
part of it. That can mean takign some odd arguments in the meantime,
some of those should probably become interfaces or properties on folder
in the long term.
To newer names better reflecting their types and yet sorting together
with folder.go. Doing it now without asking because there are no open
PRs that will get killed by it, and to avoid bikeshedding the names.