Automatically add dates to release notes

.readthedocs.yml

@@ -6,6 +6,10 @@ build:
   os: ubuntu-22.04
   tools:
     python: "3"
+  jobs:
+    post_checkout:
+    - git remote add upstream https://github.com/python-pillow/Pillow.git # For forks
+    - git fetch upstream --tags
 
 python:
   install:

docs/conf.py

@@ -28,6 +28,7 @@
 # extensions coming with Sphinx (named 'sphinx.ext.*') or your custom
 # ones.
 extensions = [
+    "dater",
     "sphinx.ext.autodoc",
     "sphinx.ext.extlinks",
     "sphinx.ext.intersphinx",

docs/dater.py

@@ -0,0 +1,50 @@
+"""
+Sphinx extension to add timestamps to release notes based on Git versions.
+
+Based on https://github.com/jaraco/rst.linker, with thanks to Jason R. Coombs.
+"""
+
+from __future__ import annotations
+
+import datetime as dt
+import re
+import subprocess
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from sphinx.application import Sphinx
+
+DOC_NAME_REGEX = re.compile(r"releasenotes/\d+\.\d+\.\d+")
+VERSION_TITLE_REGEX = re.compile(r"^(\d+\.\d+\.\d+)\n-+\n")
+
+
+def get_date_for(git_version: str) -> dt.datetime | None:
+    cmd = ["git", "log", "-1", "--format=%ai", git_version]
+    try:
+        out = subprocess.check_output(
+            cmd, stderr=subprocess.DEVNULL, text=True, encoding="utf-8"
+        )
+        ts = out.strip()
+        return dt.datetime.fromisoformat(ts)
+    except subprocess.CalledProcessError:
+        return None
+
+
+def add_date(app: Sphinx, doc_name: str, source: list[str]) -> None:
+    if DOC_NAME_REGEX.match(doc_name) and (m := VERSION_TITLE_REGEX.match(source[0])):
+        old_title = m.group(1)
+
+        if tag_datetime := get_date_for(old_title):
+            new_title = f"{old_title} ({tag_datetime:%Y-%m-%d})"
+        else:
+            new_title = f"{old_title} (unreleased)"
+
+        new_underline = "-" * len(new_title)
+
+        result = source[0].replace(m.group(0), f"{new_title}\n{new_underline}\n", 1)
+        source[0] = result
+
+
+def setup(app: Sphinx) -> dict[str, bool]:
+    app.connect("source-read", add_date)
+    return {"parallel_read_safe": True}