Regression of #29493. If a branch has been deleted, repushing it won't
restore it.
Lunny may have noticed that, but I didn't delve into the comment then
overlooked it:
https://github.com/go-gitea/gitea/pull/29493#discussion_r1509046867
The additional comments added are to explain the issue I found during
testing, which are unrelated to the fixes.
Jason Song