[API] Pull Request is null when branch was deleted

[ccaspers]

• Gitea version (or commit ref): 3b612ce
• Git version: 2.20.1
• Operating system: Linux
• Database:
  • PostgreSQL
  • MySQL
  • MSSQL
  • SQLite
• Can you reproduce the bug at https://try.gitea.io:
  • Yes (provide example URL)
  • No
  • Not relevant

When a Pull Request was merged, the API endpoint GET /api/v1/repo/<org>/<user>/pulls/<number> returns null as soon as the branch is deleted (see [1]), while the web interface still lists all information about the PR (see [2]). Recreating the branch fixes the issue. The list of all pull-requests shows the same error (see [3]).

This was already reported in #4595, but the issue was closed because there was no activity.

Examples on try.gitea.io:

• [1] faulty pull with missing branch
• [2] faulty pull in web interface
• [3] list of pulls

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs during the next 2 weeks. Thank you for your contributions.