gen_release_notes: include links in relnotes.rst when generating the new release note

This is required to allow the docs to build, which in turn is required
if we want to allow merge requests against release (staging) branches.

Cc: mesa-stable
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/20460>

bin/gen_release_notes.py

@@ -310,6 +310,31 @@ def get_features(is_point_release: bool) -> typing.Generator[str, None, None]:
         yield "None"
 
 
+def update_release_notes_index(version: str) -> None:
+    relnotes_index_path = pathlib.Path('docs') / 'relnotes.rst'
+
+    with relnotes_index_path.open('r') as f:
+        relnotes = f.readlines()
+
+    new_relnotes = []
+    first_list = True
+    second_list = True
+    for line in relnotes:
+        if first_list and line.startswith('-'):
+            first_list = False
+            new_relnotes.append(f'-  :doc:`{version} release notes <relnotes/{version}>`\n')
+        if not first_list and second_list and line.startswith('   relnotes/'):
+            second_list = False
+            new_relnotes.append(f'   relnotes/{version}\n')
+        new_relnotes.append(line)
+
+    with relnotes_index_path.open('w') as f:
+        for line in new_relnotes:
+            f.write(line)
+
+    subprocess.run(['git', 'add', relnotes_index_path])
+
+
 async def main() -> None:
     v = pathlib.Path('VERSION')
     with v.open('rt') as f:
@@ -349,6 +374,9 @@ async def main() -> None:
             return
 
     subprocess.run(['git', 'add', final])
+
+    update_release_notes_index(this_version)
+
     subprocess.run(['git', 'commit', '-m',
                     f'docs: add release notes for {this_version}'])