Gitea doesn't work with PRs that merge unrelated histories #36644

Description

When a user tries to merge two branches with unrelated histories, some links stop working (e.g
https://gitea.test/org/repo/pulls/1/files returns 400)

Gitea Version

1.25.4

Can you reproduce the bug on the Gitea demo site?

Yes

Log Gist

No response

Screenshots

No response

Git Version

No response

Operating System

No response

How are you running Gitea?

on premise instance

Database

PostgreSQL