Dan from Disqus came into IRC today asking for help to configure Arcanist to only run the linter on new changes. The context is the existing codebase has many lint errors, so it would be best if the linter only ran against lint errors the change in question introduces.
See chatlog here -- https://secure.phabricator.com/chatlog/channel/6/?at=108388
I jumped in the code and the --only-new flag is pretty complicated. I came away thinking it would voraciously lint any file with changes... Overall, I was not too helpful in getting resolution here.