Hi,
thanks a lot for your work on rustfmt. I would like to have an option to always put all imports into a single group. I tried looking for an existing issue but I might have missed one

use self::some_mod::SomeStruct;

use crate::my_module;

use diesel::prelude::*;

use rocket::serde::json::Json;

use std::env;

use uuid::Uuid;

would format to

use self::some_mod::SomeStruct;
use crate::my_module;
use diesel::prelude::*;
use rocket::serde::json::Json;
use std::env;
use uuid::Uuid;

The rationale is that I like the idea of rustfmt enforcing the grouping, but find it nicer to have them all together, ordered inside the group the way rustfmt currently does it.

If this is something that could be added to rustfmt, I could take a look at making a PR. At a glance it looks like I could just follow the implementation of the StdExternalCrate option and it wouldn't be too difficult.

As for the name, maybe something like "Together"?

group_imports = "Together"