Process for upgrading the stdlib to a new cpython version
==========================================================

.. note::

    overly detailed

0. make sure your working dir is clean
1. check out the branch vendor/stdlib-3.9
2. upgrade the files there
   2a. `rm -rf lib-python/3/*`
   2b. copy the files from the cpython repo
   2c. copy to `lib_pypy`
     - `Modules/_ctypes/_ctypes_test.c`
     - `Modules/_testcapimodule.c`
     - `Modules/_testmultiphase.c`
     - `Modules/_testmultiphase.c.h`
   2d. `hg add lib-python/3/`
   2e. `hg remove --after`
   2f. show copied files in cpython repo by running appropriate git commands
   2g. fix copies / renames manually by running `hg copy --after <from> <to>` for each copied file
3. update stdlib-version.txt with the output of `git status` from the cpython repo
4. commit
5. update to py3.9
6. create a integration branch for the new stdlib
   (just hg branch stdlib-$version)
7. merge vendor/stdlib or vendor/stdlib-3-*
8. commit
10. fix issues. Note especially changes in datetime.py, venv/__init__.py, and others.
11. commit --close-branch
14. update version numbers in sys/version.py and cpyext/include/patch_level.h

Process for updating a point release if the diff is small
=========================================================

In cpython, do `git diff -r <current> -r <newer> Lib > <outfile>`
so for instance `git diff -r v3.9.7 -r v3.9.9 Lib > /tmp/patch3.9.9`

In pypy, cd into `lib-python/3`
Then do 
patch -p2 -i <outfile>

If patch asks about reveresed patches, reply "no" and apply anyway "yes"

Carefully note the failures in the *.rej files and try to resolve the conflicts.
Delete all the *.orig files, and look for files that should be added to version control
Look for removed files that should be deleted from version control

Then update sys/version.py, cpyext/include/patchlevel.h, and ./stdlib-version.txt

Make sure binary files (especially pip and setuptools wheels) were copied
correctly. On at least one occasion they were empty after this process.
Make sure binary files (especially pip and setuptools wheels) were copied
correctly. On at least one occasion they were empty after this process.