Allow `--edition 2021` to be passed to rustfmt
This was added to Configurations.md in but the option wasn't
actually made available. This should let people who are using Rust 2021
on nightly rustc run `cargo fmt` again.
@@ -689,6 +689,7 @@ fn edition_from_edition_str(edition_str: &str) -> Result<Edition> {
match edition_str {
"2015" => Ok(Edition::Edition2015),
"2018" => Ok(Edition::Edition2018),
+ "2021" => Ok(Edition::Edition2021),
_ => Err(format_err!("Invalid value for `--edition`")),
}
}
