In 0.8.1, the elm-version is auto-detected based on the presence of elm.json or elm-package.json in the current working directory.

Proposal: instead of checking the current working directory, for each file check the file's folder and if not found traverse upwards until a package file is found.

It seems like this would be more flexible, and still do the right thing in all current cases? I think this would also allow plugins to not have to pass --elm-version unless they are using --stdin