Rollup merge of #46787 - varkor:contrib-6, r=QuietMisdreavus

Add an option to allow rustdoc to list modules by appearance

The `--sort-modules-by-appearance` option will list modules in the
order that they appear in the source, rather than sorting them
alphabetically (as is the default). This resolves #8552.

src/test/rustdoc/sort-modules-by-appearance.rs

@@ -0,0 +1,23 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Tests the rustdoc --sort-modules-by-appearance option, that allows module declarations to appear
+// in the order they are declared in the source code, rather than only alphabetically.
+
+// compile-flags: -Z unstable-options --sort-modules-by-appearance
+
+pub mod module_b {}
+
+pub mod module_c {}
+
+pub mod module_a {}
+
+// @matches 'sort_modules_by_appearance/index.html' '(?s)module_b.*module_c.*module_a'
+// @matches 'sort_modules_by_appearance/sidebar-items.js' '"module_b".*"module_c".*"module_a"'