Trouble accessing file differences in private repositories

[Sonali-Behera-TRT]

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Issue Description:

I'm encountering an issue with my GitHub Webhook setup where file differences aren't being fetched when transitioning a repository's visibility from public to private. Although the webhook functions smoothly for public repositories, it fails to deliver the expected file changes for private ones. Despite creating a new PR in both public and private repositories, the webhook still doesn't fetch file differences via the provided webhook payload URLs (https://patch-diff.githubusercontent.com/raw/{owner}/{repo}/pull/{pr_number}.diff or https://github.com/{owner}/{repo}/pull/{pr_number}.diff). Additionally, I'm passing a token in the API header (https://api.github.com/app/installations/{installation_id}/access_tokens), but I'm consistently receiving a 404 error stating "Not Found." I've ensured that the app has been granted all necessary permissions, including owner permissions where applicable.

Background Information:

• I've implemented GitHub Webhooks to automate processes in my project repository.
• The webhook is set up to trigger on the creation of a new PR.
• I've developed the webhook handler using Python.
• Due to the sensitivity of the project, private repositories are used.

Expected Outcome:

I expect to receive file differences in the same manner for both public and private repositories when a new PR event is triggered.

Current Outcome:

While the webhook successfully triggers on PR events, the file differences are reported as "Not Found" when attempting to access them via the diff_url in the specified format.

Versions and Environment:

• Programming Language/Framework: Python
• Repository Visibility: Private

Request for Assistance:

I would greatly appreciate any insights or suggestions on how to troubleshoot and resolve this issue. Additionally, if anyone has faced similar challenges or has alternative approaches to achieve the desired functionality, I'm open to suggestions.

Thank you in advance for your assistance!