Disallow regressing crate docs

crates/ra_fmt/src/lib.rs

@@ -1,5 +1,7 @@
 //! This crate provides some utilities for indenting rust code.
-//!
+
+use std::iter::successors;
+
 use itertools::Itertools;
 use ra_syntax::{
     ast::{self, AstNode, AstToken},
@@ -7,7 +9,6 @@ use ra_syntax::{
     SyntaxKind::*,
     SyntaxNode, SyntaxToken, T,
 };
-use std::iter::successors;
 
 pub fn reindent(text: &str, indent: &str) -> String {
     let indent = format!("\n{}", indent);