ci: add sync-upstream workflow

[piyoki]

Background

Add sync-upstream workflow back, but this time, let's do NOT add the broken PR create action. Instead, let @daeBot automate the PR creation for us.

Checklist

• The Pull Request has been fully tested
• There's an entry in the CHANGELOG
• There is a user-facing docs PR against https://github.com/daeuniverse/daed

Full changelog

• ci: add sync-upstream workflow

Mock

Try to reproduce the test scenario as much as I could...

Expected Outcome

• The sync-upstream workflow in daed-1 is kicked off
• daebot creates a pull_request after the workflow run has been completed

Reproduction

1.1 checkout to a specific history commit in dae-wing submodule

1.2 kick off the sync-upstream workflow by pushing a commit to ci-bot-experiment origin/main

Note: In the production case, we should use dae-wing.

1.3 create a PR on the fly

Issue reference

NA

[kunish]

Sounds really great. But we need more evidence showing this would work as expected before merging.

[piyoki]

Sounds really great. But we need more evidence showing this is working as expected before merging.

Sure, let me work on the bot automation part.

[piyoki]

Result: daeuniverse#1

[kunish]

LGTM :)