Show "breadcrumbs" on wiki pages

tildes/scss/modules/_breadcrumbs.scss

@@ -0,0 +1,14 @@
+ol.breadcrumb,
+ul.breadcrumb {
+  margin-left: 0;
+  font-size: 0.6rem;
+  line-height: 0.8rem;
+
+  a {
+    text-decoration: none;
+
+    &:hover {
+      text-decoration: underline;
+    }
+  }
+}

tildes/scss/styles.scss

@@ -9,6 +9,7 @@
 @import "base";
 @import "layout";
 
+@import "modules/breadcrumbs";
 @import "modules/btn";
 @import "modules/chip";
 @import "modules/comment";

tildes/tildes/models/group/group_wiki_page.py

@@ -4,8 +4,8 @@
 """Contains the GroupWikiPage class."""
 
 from datetime import datetime
-from pathlib import Path
-from typing import Any, Optional, Sequence, Tuple
+from pathlib import Path, PurePath
+from typing import Any, List, Optional, Sequence, Tuple
 
 from pygit2 import Repository, Signature
 from pyramid.security import Allow, DENY_ALL, Everyone
@@ -104,6 +104,19 @@ class GroupWikiPage(DatabaseModel):
         """Return the page's slug, which is also its filename with no extension."""
         return self.file_path.stem
 
+    @property
+    def folders(self) -> List[PurePath]:
+        """Return a list of the folders the page is inside (if any)."""
+        path = PurePath(self.path)
+
+        # the last element of .parents will be ".", chop that off
+        folders = list(path.parents)[:-1]
+
+        # reverse the list, since .parents goes "upwards" towards root
+        folders.reverse()
+
+        return folders
+
     @property
     def history_url(self) -> str:
         """Return a url to the page's edit history."""

tildes/tildes/templates/base.jinja2

@@ -84,6 +84,8 @@
 
 <main class="{% block main_classes %}{% endblock %}" data-js-hide-sidebar-if-open>
 
+{% block pre_main_heading %}{% endblock %}
+
 {# Only output the <h1> tag if the main_heading block has some content #}
 {% set main_heading %}{% block main_heading %}{% endblock %}{% endset %}
 {% if main_heading %}

tildes/tildes/templates/group_wiki_page.jinja2

@@ -13,6 +13,19 @@
 
 {% block main_classes %}text-formatted text-wiki{% endblock %}
 
+{% block pre_main_heading %}
+<ol class="breadcrumb">
+  <li class="breadcrumb-item">
+    <a href="{{ request.route_url("group_wiki", group_path=page.group.path) }}">~{{ page.group.path }} wiki</a>
+  </li>
+  {% for folder in page.folders %}
+    <li class="breadcrumb-item">
+      <a href="{{ request.route_url("group_wiki_page", group_path=page.group.path, wiki_page_path=folder|string) }}">{{ folder.name }}</a>
+    </li>
+  {% endfor %}
+</ol>
+{% endblock %}
+
 {% block main_heading %}{{ page.page_name }}{% endblock %}
 
 {% block content %}