Fetch changes from `upstream` github.com/microsoft/fluentui

Road to v9 stable roadmap:

Local machine setup

Prerequisit:

you have the origin and upstream remotes configured per the [setup instructions](https://github.com/microsoft/fluentui/wiki/Setup#setting-the-upstream-remote

# Fetch changes from `upstream` github.com/microsoft/fluentui
git fetch upstream
# Create a local `9.0-rc` branch starting from the upstream `9.0-rc` branch
git checkout upstream/9.0-rc
# Get latest changes to your local machine
git pull upstream 9.0-rc
# Branch out from 9.0-rc and start developing
git checkout -b <my-branch-name>

PR workflow setup

1. Push your branch changes

git push -u origin <my-branch-name>

2. Create PR against 9.0-rc

3. After CI passes and you got all required approval. Merge

Getting updates back to master

Based on your contribution to 9.0-rc branch it might be required to get the fix/change it to master ASAP. If that's the case, please create a PR against master via chery-pick of particular commit. The PR workflow follows standard practices.

Merging 9.0-rc back to master/ End of life

To merge back to master following workflow should be applied:

1. checkout 9.0-rc branch and fetch latest updates to your local machine
2. drop following commits (you can use git rebase -i for example):

• 1st commit - enabling automatic PR pipeline runs.
• 2nd commit - setting beachball branch
  • NOTE: this one is not merged yet thus linking PR that will originate the commit hash

3. if you used rebase you'll need to force push.
4. create PR against master
5. once the pipeline passes and you get approval, merge
6. delete 9.0-rc