Use release-cycle data for main branch version

Author: corneliusroemer

conf.py

@@ -1,3 +1,5 @@
+import json
+
 extensions = [
     'notfound.extension',
     'sphinx.ext.extlinks',
@@ -185,6 +187,14 @@
 
 """
 
+# Dynamically expose the Python version associated with the "main" branch.
+with open("include/release-cycle.json", encoding="UTF-8") as _f:
+    _cycle = json.load(_f)
+_main_version = next(
+    ver for ver, data in _cycle.items() if data.get("branch") == "main"
+)
+rst_prolog += f"\n.. |mainversion| replace:: {_main_version}\n"
+
 # sphinx.ext.extlinks
 # This config is a dictionary of external sites,
 # mapping unique short aliases to a base URL and a prefix.

versions.rst

@@ -5,7 +5,7 @@
 Status of Python versions
 =========================
 
-The ``main`` branch is currently the future Python 3.14, and is the only
+The ``main`` branch is currently the future Python |mainversion|, and is the only
 branch that accepts new features.  The latest release for each Python
 version can be found on the `download page <https://www.python.org/downloads/>`_.