Docs: Allow unlimited multi-level navigation (just-the-docs#1440)

* Remove `jekyll-default-layout` plugin

* Move docs/navigation-structure to docs/navigation

* Fix uses of line-nos in md files

* Update CHANGELOG.md

---------

Co-authored-by: Matt Wang <[email protected]>

CHANGELOG.md

@@ -23,9 +23,10 @@ Code changes to `main` that are *not* in the latest release:
 
 Docs changes made since the latest release:
 
-- N/A
+- Added: Allow unlimited multi-level navigation by [@pdmosses] in [#1440]
 
 [#1431]: https://github.com/just-the-docs/just-the-docs/pull/1431
+[#1440]: https://github.com/just-the-docs/just-the-docs/pull/1440
 
 ## Release v0.9.0
 

MIGRATION.md

@@ -41,7 +41,7 @@ This document contains instructions on how to migrate and upgrade Just the Docs
 > and pull the changes of a new release to your clone,
 > you may need to resolve merge conflicts.
 
-[CHANGELOG]: {{ site.baseurl }}{% link CHANGELOG.md %}
+[CHANGELOG]: {% link CHANGELOG.md %}
 
 ## v0.6.x - v0.7.0
 
@@ -373,7 +373,7 @@ For changes since v0.3.3, the log usually references the merged PR that made the
 
 #### Configuration
 
-- Mermaid support: first-class support for [Mermaid](https://mermaid.js.org/) - a JavaScript-based diagram and charting tool supported by GitHub - has been added to the theme. **This feature is opt-in.** See the new doc subsections in [Configuration]({% link docs/configuration.md %}#mermaid-diagrams) and [Code]({% link docs/ui-components/code.md %}#mermaid-diagram-code-blocks) for more.
+- Mermaid support: first-class support for [Mermaid](https://mermaid.js.org/) - a JavaScript-based diagram and charting tool supported by GitHub - has been added to the theme. **This feature is opt-in.** See the new doc subsections in [Configuration]({% link docs/configuration.md %}#mermaid-diagrams) and [Code]({% link docs/ui-components/code/index.md %}#mermaid-diagram-code-blocks) for more.
 - Multiple Google Analytics tags are now supported. PR: [#1029]
 
 #### Customization

_config.yml

@@ -21,6 +21,14 @@ repository: just-the-docs/just-the-docs # for github-metadata
 
 permalink: pretty
 
+defaults:
+  -
+    scope:
+      path: "docs" # an empty string here means all files in the project
+      type: "pages"
+    values:
+      layout: "default"
+
 exclude:
  # from https://github.com/jekyll/jekyll/blob/master/lib/site_template/_config.yml:
    - .sass-cache/

docs/configuration.md

@@ -1,5 +1,4 @@
 ---
-layout: default
 title: Configuration
 nav_order: 2
 ---
@@ -87,7 +86,7 @@ mermaid:
 
 Provide a `path` instead of a `version` key to load the mermaid library from a local file.
 
-See [the Code documentation]({% link docs/ui-components/code.md %}#mermaid-diagram-code-blocks) for more configuration options and information.
+See [the Code documentation]({% link docs/ui-components/code/index.md %}#mermaid-diagram-code-blocks) for more configuration options and information.
 
 ## Aux links
 
@@ -126,7 +125,7 @@ New (v0.4.0)
 {: .label .label-green }
 
 External links can be added to the navigation through the `nav_external_links` option.
-See [Navigation Structure]({% link docs/navigation-structure.md %}#external-navigation-links) for more details.
+See [Navigation Structure]({% link docs/navigation/main/external.md %}) for more details.
 
 ## Footer content
 

docs/customization.md

@@ -1,5 +1,4 @@
 ---
-layout: default
 title: Customization
 nav_order: 6
 ---
@@ -178,7 +177,7 @@ New (v0.4.0)
 
 `_includes/toc_heading_custom.html`
 
-If the page has any child pages, and `has_toc` is not set to `false`, this content appears as a heading above the [auto-generating list of child pages]({% link docs/navigation-structure.md %}#auto-generating-table-of-contents) after the page's content.
+If the page has any child pages, and `has_toc` is not set to `false`, this content appears as a heading above the [auto-generating list of child pages]({% link docs/navigation/children.md %}) after the page's content.
 
 #### Example
 {: .no_toc }

docs/index-test.md

@@ -1,5 +1,4 @@
 ---
-layout: default
 title: Markdown kitchen sink
 nav_order: 99
 ---

docs/layout/layout.md

@@ -2,7 +2,6 @@
 title: Layout
 layout: default
 nav_order: 4.5
-has_children: true
 ---
 
 # Layout
@@ -18,11 +17,11 @@ You can use [Jekyll's front matter defaults] to specify the same layout for many
 
 ## The `default` layout
 
-This page uses the default layout.
+This page uses the default layout. This site configures `layout: default` as a [front matter default](https://jekyllrb.com/docs/configuration/front-matter-defaults/) value for all pages in the `docs` directory.
 
-It is a *responsive* layout: on medium and larger width displays, it displays a sidebar, including a navigation panel; on smaller width displays, the sidebar is automatically hidden under a button.
+The default layout of Just the Docs is a *responsive* layout: on medium and larger width displays, it displays a sidebar, including a navigation panel; on smaller width displays, the sidebar is automatically hidden under a button.
 
-Each child (and grandchild) page of a top-level page has so-called *breadcrumbs*: links to its parent (and grandparent) pages. It shows the breadcrumbs above the main content of the page.
+All pages except top-level pages automatically have a list of  so-called *breadcrumbs*: links to their parent pages and any higher-level ancestors. They show the breadcrumbs above the main content of the page.
 
 Each page that has child pages generally has a list of links to those pages (you can suppress it by `has_toc: false` in the front matter). It shows the list as a *table of contents* below the main content.
 

docs/layout/minimal/minimal.md

@@ -2,7 +2,6 @@
 title: A minimal layout page
 layout: minimal
 parent: Layout
-has_children: true
 ---
 
 # A minimal layout page