Track 3.9 instead of 3.10?

[Chris Angelico]

On Wed, Jul 28, 2021 at 1:05 AM Skip Montanaro <skip.montanaro at gmail.com> wrote:
>
> I have a development branch in my fork of python/cpython, the
> register2 branch of https://github.com/smontanaro/cpython. As I am
> dealing with virtual machine internals I've found the changes to the
> virtual machine between 3.9 and 3.10 too disruptive. I'd like to track
> 3.9 instead. How would I go about making the switch while minimizing
> the number of (inevitable) conflicts? I was thinking of diffing my
> current state against 3.10, then creating a new branch off 3.9 and
> applying the diff to that. That makes most of the effort outside of
> the view of git though, and won't necessarily minimize conflicts. Is
> there some way to do this totally within the git infrastructure?
>

If your changes (on top of 3.10) aren't too invasive, you could rebase
those changes on top of 3.9, or cherry-pick them one by one. That
would be a more granular way to "diff [your] current state against
3.10" (assuming you've been making those changes as individual
commits).

Check out the "rebase --onto" operation:

https://git-scm.com/docs/git-rebase

The first example of --onto (regarding master/next/topic branches) is
what I think you're trying to do.

ChrisA