Provide MD checklists for the changelog (#1937)

* Output changelog checklists

Fixes: #1682
Signed-off-by: Johannes Marbach <n0-0ne+github@mailbox.org>

changelogs/header.md

@@ -6,11 +6,10 @@ Variables:
     DATE     = Replaced by the date (eg: April 01, 2021)
 -->
 
-## VERSION
-
 <table class="release-info">
 <tr><th>Git commit</th><td><a href="https://github.com/matrix-org/matrix-spec/tree/VERSION">https://github.com/matrix-org/matrix-spec/tree/VERSION</a></td>
 <tr><th>Release date</th><td>DATE</td>
+<tr><th>Checklist</th><td><a href="/changelog/VERSION/checklist.md">checklist.md</a></td>
 </table>
 
 <!-- Intentionally blank line to ensure headers work in the concatenated changelog -->

changelogs/internal/newsfragments/1937.clarification

@@ -0,0 +1 @@
+Provide markdown checklists for changelogs under `/changelog/$VERSION/checklist.md`.

changelogs/template.md.jinja

@@ -1,7 +1,7 @@
 {% for section_name, section in sections.items() %}
 {% if section_name %}
 
-### {{section_name}}
+## {{section_name}}
 {% endif %}
 
 {% if section %}