bin/gen_release_notes: automatically commit release notes

Cc: mesa-stable
Signed-off-by: Eric Engestrom <eric@engestrom.ch>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5833>

bin/gen_release_notes.py

@@ -25,6 +25,7 @@ import asyncio
 import datetime
 import os
 import pathlib
+import subprocess
 import sys
 import textwrap
 import typing
@@ -252,6 +253,10 @@ async def main() -> None:
         except:
             print(exceptions.text_error_template().render())
 
+    subprocess.run(['git', 'add', final])
+    subprocess.run(['git', 'commit', '-m',
+                    f'docs: add release notes for {this_version}'])
+
 
 if __name__ == "__main__":
     loop = asyncio.get_event_loop()