overwrite html files for multilevel

_includes/components/breadcrumbs.html

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+{%- comment -%}
+  Include as: {%- include components/breadcrumbs.html -%}
+  Depends on: page, site.
+  Includes: components/site_nav.html.
+  Results in: HTML for the breadcrumbs component.
+  Overwrites:
+    nav_list_link, site_nav, nav_list_simple, nav_list_link_class, nav_category,
+    nav_anchor_splits, nav_breadcrumbs, nav_split, nav_split_next, nav_split_test,
+    nav_breadcrumb_link, nav_list_end_less, nav_list_end_count, nav_end_index, nav_breadcrumb.
+{%- endcomment -%}
+
+{%- if page.url != "/" and page.parent and page.title -%}
+
+{%- capture site_nav -%}
+{%- include_cached components/site_nav.html all=true -%}
+{%- endcapture -%}
+
+{%- capture nav_list_link -%}
+<a href="{{ page.url | relative_url }}" class="nav-list-link">
+{%- endcapture -%}
+
+{%- capture nav_list_simple -%}
+<ul class="nav-list">
+{%- endcapture -%}
+
+{%- capture nav_list_link_class %} class="nav-list-link">
+{%- endcapture -%}
+
+{%- capture nav_category -%}
+<div class="nav-category">
+{%- endcapture -%}
+
+{%- assign nav_anchor_splits =
+      site_nav | split: nav_list_link |
+      first | split: nav_category |
+      last | split: "</a>" -%}
+
+{%- comment -%}
+  The ordinary pages (if any) and the collections pages (if any) are separated by
+  occurrences of nav_category.
+
+  Any ancestor nav-links of the page are contained in the last group of pages,
+  immediately preceding nav-lists. After splitting at "</a>", the anchor that
+  was split is a potential ancestor link when the following split starts with
+  a nav-list. 
+
+  The array nav_breadcrumbs is the stack of current potential ancestors of the
+  current page. A split that contains one or more "</ul>"s requires that number
+  of potential ancestors to be popped from the stack.
+
+  The number of occurrences of a string in nav_split_next is computed by removing
+  them all, then dividing the resulting size difference by the length of the string.
+{%- endcomment %}
+
+{%- assign nav_breadcrumbs = "" | split: "" -%}
+
+{%- for nav_split in nav_anchor_splits -%}
+{%- unless forloop.last -%}
+
+{%- assign nav_split_next = nav_anchor_splits[forloop.index] | strip -%}
+
+{%- assign nav_split_test =
+      nav_split_next | remove_first: nav_list_simple | prepend: nav_list_simple -%}
+{%- if nav_split_test == nav_split_next -%}
+  {%- assign nav_breadcrumb_link =
+        nav_split | split: "<a " | last | prepend: "<a " |
+        replace: nav_list_link_class, ">" | append: "</a>" -%}
+  {%- assign nav_breadcrumbs = nav_breadcrumbs | push: nav_breadcrumb_link -%}
+{%- endif -%}
+
+{%- if nav_split_next contains "</ul>" -%}
+  {%- assign nav_list_end_less = nav_split_next | remove: "</ul>" -%}
+  {%- assign nav_list_end_count =
+        nav_split_next.size | minus: nav_list_end_less.size | divided_by: 5 -%}
+  {% for nav_end_index in (1..nav_list_end_count) %}
+    {%- assign nav_breadcrumbs = nav_breadcrumbs | pop -%}
+  {%- endfor -%}
+{%- endif -%}
+
+{%- endunless -%}
+{%- endfor -%}
+
+<nav aria-label="Breadcrumb" class="breadcrumb-nav">
+  <ol class="breadcrumb-nav-list">
+    {%- for nav_breadcrumb in nav_breadcrumbs %}
+    <li class="breadcrumb-nav-list-item">{{ nav_breadcrumb }}</li>
+    {%- endfor %}
+    <li class="breadcrumb-nav-list-item"><span>{{ page.title }}</span></li>
+  </ol>
+</nav>
+
+{% if site.nav_error_report %}
+{{ nav_error_report }}
+{% endif %}
+
+{%- endif -%}

_includes/components/children_nav.html

@@ -0,0 +1,90 @@
+{%- comment -%}
+  Include as: {%- include components/children_nav.html -%}
+  Depends on: page, site, nav_breadcrumbs.
+  Results in: HTML for the children-navigation component.
+  Includes: components/nav/sorted.html, toc_heading_custom.html.
+  Overwrites:
+    nav_ancestor_links, nav_top_node_titles, nav_child_candidates, nav_children,
+    nav_child, nav_child_ok, nav_child_ancestor, nav_sorted.
+{%- endcomment -%}
+
+{%- comment -%}
+  Whether a page has any children is checked efficiently by inspecting the cached
+  site_nav. If the page has no children, nav_children is set to an empty array;
+  otherwise nav_children is left unset. (The site_nav is rendered the first time
+  it is included, and that may overwrite various variables.)
+{%- endcomment -%}
+
+{%- if page.has_children == false -%}
+  {%- assign nav_children = "" | split: "" -%}
+{%- else -%}
+
+  {%- capture site_nav -%}
+  {%- include_cached components/site_nav.html all=true -%}
+  {%- endcapture -%}
+
+  {%- assign nav_children = nil -%}
+
+  {%- capture nav_list_link -%}
+  <a href="{{ page.url | relative_url }}" class="nav-list-link">
+  {%- endcapture -%}
+
+  {%- capture nav_list_simple -%}
+  <ul class="nav-list">
+  {%- endcapture -%}
+
+  {%- assign nav_child_start = site_nav
+        | split: nav_list_link | last
+        | split: "</a>" | slice: 1 | first -%}
+
+  {%- assign nav_child_test = nav_child_start 
+        | remove_first: nav_list_simple | prepend: nav_list_simple -%}
+
+  {%- if nav_child_start != nav_child_test -%}
+    {%- assign nav_children = "" | split: "" -%}
+  {%- endif -%}
+
+{%- endif -%}
+
+{%- unless nav_children -%}
+
+  {%- comment -%}
+    The layout is assumed to include components/breadcrumbs.html before this file,
+    otherwise it needs to be included here.
+  {%- endcomment -%}
+
+  {%- assign nav_ancestors = "" | split: "" -%}
+  {%- for nav_link in nav_breadcrumbs -%}
+    {%- assign nav_title = nav_link | split: ">" | slice: 1 | first | append: ">" | remove: "</a>" -%}
+    {%- assign nav_ancestors = nav_ancestors | push: nav_title -%}
+  {%- endfor -%}
+
+  {%- assign nav_parenthood = site[page.collection] | default: site.html_pages
+    | where_exp: "item", "item.title != nil" | group_by: "parent" -%}
+
+  {%- assign nav_top_nodes = nav_parenthood
+      | where_exp: "item", "item.name == ''" | map: "items" | first -%}
+
+  {% assign nav_top_node_titles = nav_top_nodes | map: "title" -%}
+
+  {%- include components/nav/children.html node=page ancestors=nav_ancestors all=true -%}
+
+{%- endunless -%}
+
+{%- if nav_children.size >= 1 -%}
+
+  {%- if page.child_nav_order == 'desc' or page.child_nav_order == 'reversed' -%}
+    {%- assign nav_children = nav_children | reverse -%}
+  {%- endif -%}
+
+<hr>
+{% include toc_heading_custom.html %}
+<ul>
+  {% for nav_child in nav_children %}
+  <li>
+    <a href="{{ nav_child.url | relative_url }}">{{ nav_child.title }}</a>{% if nav_child.summary %} - {{ nav_child.summary }}{% endif %}
+  </li>
+  {% endfor %}
+</ul>
+
+{%- endif -%}