Merge pull request rust-lang#3134 from otavio/issue-3104

Stabilize `edition` configuration option

Author: nrc

Configurations.md

@@ -2275,7 +2275,7 @@ Specifies which edition is used by the parser.
 
 - **Default value**: `2015`
 - **Possible values**: `2015`, `2018`
-- **Stable**: No
+- **Stable**: Yes
 
 ### Example
 

src/config/mod.rs

@@ -110,7 +110,7 @@ create_config! {
         "Maximum number of blank lines which can be put between items";
     blank_lines_lower_bound: usize, 0, false,
         "Minimum number of blank lines which must be put between items";
-    edition: Edition, Edition::Edition2015, false, "The edition of the parser (RFC 2052)";
+    edition: Edition, Edition::Edition2015, true, "The edition of the parser (RFC 2052)";
 
     // Options that can change the source code beyond whitespace/blocks (somewhat linty things)
     merge_derives: bool, true, true, "Merge multiple `#[derive(...)]` into a single one";