See also: #523, #545

I think it would be the right thing to traverse directories upwards, and I'm under the impression that this is what Git and many other tools do too. But not 100% confident about all edge cases that may come up. I'd say, ask a few very experienced programmers if there are any problems with it, and if none of them come up with anything, just do it 😄

(Moved comments about --stdin to a separate issue, #563)

Doing the version check separately for each file given on the command line would definitely be the right thing, since they may (in principle, at least) be from different Elm projects.

And to make sure that --elm-version can be given only once so people don't think they can do things like elm-format --elm-version 0.18 foo.elm --elm-version 0.19 bar.elm. The check currently seems to be in place (the error message is a bit misleading, Invalid option '--elm-version', but that's probably ok).

Love this. I have done the same thing for my small Atom plugin that runs elm-analyse back in 0.18.
https://github.com/ymtszw/linter-elm-analyse/blob/master/index.js#L58
In my case it was (1) traverse directories upward until it finds elm-package.json, (2) if found, set CWD there, (3) otherwise bail out.

I haven't heard anyone bring this up in a long time, I'm guessing because very few folks have both 0.18 and 0.19 projects anymore? If anyone thinks this would still be useful, please chime in.