Docs: a start on an 'improve this page' feature

Doc/improvepage.rst

@@ -0,0 +1,39 @@
+:orphan:
+
+.. _improve-a-page:
+
+****************************
+Improve a documentation page
+****************************
+
+.. only:: html and not epub
+
+   .. raw:: html
+
+      <script>
+         document.addEventListener('DOMContentLoaded', () => {
+            const params = new URLSearchParams(window.location.search);
+            document.body.innerHTML = document.body.innerHTML
+               .replace(/PAGETITLE/g, params.get('pagetitle'))
+               .replace(/PAGEURL/g, params.get('pageurl'))
+               .replace(/PAGESOURCE/g, params.get('pagesource'));
+         });
+      </script>
+
+We are always interested to hear about ways to improve the documentation.
+
+You were reading "PAGETITLE" at `<PAGEURL>`_.  The source for that page is on
+`GitHub <https://github.com/python/cpython/blob/main/Doc/PAGESOURCE?plain=1>`_.
+
+You have a few options for asking questions or suggesting changes:
+
+- You can start a discussion about the page on the Python discussion forum.
+  This link will start a pre-populated topic:
+  `Question about "PAGETITLE" <https://discuss.python.org/new-topic?category=documentation&title=Question+about+%22PAGETITLE%22&body=About+the+page+at+PAGEURL%3A>`_.
+
+- You can open an issue on the Python GitHub issue tracker. This link will
+  create a new issue pre-populated with some information for you:
+  `Docs: problem with "PAGETITLE" <https://github.com/python/cpython/issues/new?title=Docs%3A+problem+with+%22PAGETITLE%22&labels=docs&body=The+page+at+PAGEURL+has+a+problem%3A>`_.
+
+- You can `edit the page on GitHub <https://github.com/python/cpython/blob/main/Doc/PAGESOURCE?plain=1>`_
+  and open a pull request, though you will need to have signed a contributor agreement before it can be merged.

Doc/tools/templates/customsourcelink.html

@@ -1,10 +1,22 @@
 {%- if show_source and has_source and sourcename %}
+  <script>
+    document.addEventListener('DOMContentLoaded', () => {
+        const title = document.querySelector('meta[property="og:title"]').content;
+        const elements = document.querySelectorAll('.improvepage');
+        elements.forEach(element => {
+            const url = new URL(element.href);
+            url.searchParams.set('pagetitle', title);
+            element.href = url.toString();
+        });
+    });
+  </script>
   <div role="note" aria-label="source link">
     <h3>{{ _('This page') }}</h3>
     <ul class="this-page-menu">
       <li><a href="{{ pathto('bugs') }}">{% trans %}Report a bug{% endtrans %}</a></li>
+      <li><a class="improvepage" href="{{ pathto('improvepage') }}?pageurl=https://docs.python.org/3/{{ pagename }}.html&pagesource={{ sourcename|replace('.rst.txt', '.rst') }}">{% trans %}Improve this page{% endtrans %}</a></li>
       <li>
-        <a href="https://github.com/python/cpython/blob/main/Doc/{{ sourcename|replace('.rst.txt', '.rst') }}"
+        <a href="https://github.com/python/cpython/blob/main/Doc/{{ sourcename|replace('.rst.txt', '.rst?plain=1') }}"
             rel="nofollow">{{ _('Show source') }}
         </a>
       </li>