How should plugins deal with different projects?

From slack:

> chadtech [7:07 AM]
> Some times I need to make contributions to projects that dont use elm-format, and then I save and change a huge chunk of all the lines in the project.
>
> Is there a way to turn elm-format off? The only way Ive turned it off so far was by temporarily deleting my Elm sublime package. (edited)
>
> ilias [7:16 AM]
> Some editor integrations allow this. I think in sublime you can exclude files based on a regex, though temporarily disabling "format on save" seems easier. Note that quite often, it's not that a project doesn't use elm-format, but rather uses an older version of elm-format. Quite often 0.6 vs 0.7, in part due to the latter needing `@exp` to install
>
> av [6:03 PM]
> I know in Atom, you can disable the plugin instead of uninstalling it; maybe sublime has something similar?
> I think that's an interesting question in general, and I'm not sure of the best way to solve it. Should plugins keep a setting per-project? Should plugins know about both the normal and the exp releases? Maybe plugins should detect when a project isn't formatted, and either prompt you to format and commit first, or disable formatting for the project?

No files, tests, or entry points are identified. Start by clarifying whether per-project settings, version detection, or a way to disable formatting is in scope; done would be an agreed plugin behavior for projects with different elm-format usage or versions.

Written by the indexing model from the issue text.