fix: GitHubRepoForker should check if branch is accessible before continuing

[julian-risch]

Related Issues

I ran into 404 errors when using the GitHub Forker. The fork was always created correctly but the error was raised. When the fork is created it still takes a few seconds before the branch becomes accessible. _check_fork_status only checked for the repo to exist until now. This PR extends the check to also ensure the branch is accessible.

/usr/local/lib/python3.11/dist-packages/haystack_integrations/components/connectors/github/repo_forker.py in run(self, url)
    297                 logger.info(f"Creating branch for issue #{issue_number}")
--> 298                 self._create_issue_branch(fork_path, issue_number)
    299 

...

PipelineRuntimeError: The following component failed to run:
Component name: 'repo_forker'
Component type: 'GitHubRepoForker'
Error: 404 Client Error: Not Found for url: https://api.github.com/repos/haystack-demo-user/haystack-core-integrations/git/ref/heads/main

Proposed Changes:

• Extend _check_fork_status and check that only the forked repo is accessible but also its branches.

How did you test it?

Notes for the reviewer

Checklist

• I have read the contributors guidelines and the code of conduct
• I have updated the related issue with new insights and changes
• I added unit tests and updated the docstrings
• I've used one of the conventional commit types for my PR title: fix:, feat:, build:, chore:, ci:, docs:, style:, refactor:, perf:, test:.