feat(v2): auto-generated sidebars, frontmatter-less sites (#4582)

* POC of autogenerated sidebars

* use combine-promises utility lib

* autogenerated sidebar poc working

* Revert "autogenerated sidebar poc working"

This reverts commit c81da980

* POC of auto-generated sidebars for community docs

* update tests

* add initial test suite for autogenerated sidebars + fix some edge cases

* Improve autogen sidebars: strip more number prefixes in folder breadcrumb + slugs

* fix typo!

* Add tests for partially generated sidebars + fix edge cases + extract sidebar generation code

* Ability to read category metadatas file from a file in the category

* fix tests

* change position of API

* ability to extract number prefix

* stable system to enable position frontmatter

* fix tests for autogen sidebar position

* renamings

* restore community sidebars

* rename frontmatter position -> sidebar_position

* make sidebarItemsGenerator fn configurable

* minor changes

* rename dirPath => dirName

* Make the init template use autogenerated sidebars

* fix options

* fix docusaurus site: remove test docs

* add _category_ file to docs pathsToWatch

* add _category_ file to docs pathsToWatch

* tutorial: use sidebar_position instead of file number prefixes

* Adapt Docusaurus tutorial for autogenerated sidebars

* remove slug: /

* polish the homepage template

* rename _category_ sidebar_position to just "position"

* test for custom sidebarItemsGenerator fn

* fix category metadata + add link to report tutorial issues

* fix absolute path breaking tests

* fix absolute path breaking tests

* Add test for floating number sidebar_position

* add sidebarItemsGenerator unit tests

* add processSidebars unit tests

* Fix init template broken links

* windows test

* increase code translations test timeout

* cleanup mockCategoryMetadataFiles after windows test fixed

* update init template positions

* fix windows tests

* fix comment

* Add autogenerated sidebar items documentation + rewrite the full sidebars page doc

* add useful comment

* fix code block title

packages/docusaurus-init/templates/classic/sidebars.js

@@ -1,22 +1,26 @@
+/**
+ * Creating a sidebar enables you to:
+ - create an ordered group of docs
+ - render a sidebar for each doc of that group
+ - provide next/previous navigation
+
+ The sidebars can be generated from the filesystem, or explicitly defined here.
+
+ Create as many sidebars as you want.
+ */
+
 module.exports = {
-  tutorial: [
+  // By default, Docusaurus generates a sidebar from the docs folder structure
+  tutorialSidebar: [{type: 'autogenerated', dirName: '.'}],
+
+  // But you can create a sidebar manually
+  /*
+  tutorialSidebar: [
     {
       type: 'category',
-      label: 'Tutorial - Basics',
-      items: [
-        'getting-started',
-        'create-a-page',
-        'create-a-document',
-        'create-a-blog-post',
-        'markdown-features',
-        'deploy-your-site',
-        'congratulations',
-      ],
-    },
-    {
-      type: 'category',
-      label: 'Tutorial - Extras',
-      items: ['manage-docs-versions', 'translate-your-site'],
+      label: 'Tutorial',
+      items: ['hello'],
     },
   ],
+   */
 };