Wrong `default branch` while switching between branches via the web interface

[lng2020]

Description

When switching between branches via the web interface, the default branch should remain unchanged.

e.g. The default branch should remain main

Gitea Version

latest codebase

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?

building Gitea from source code

Database

None

[CaiCandong]

@yp05327

[lng2020]

caused by pr #26697

[yp05327]

$defaultBranch is not the repo's default branch, the naming of this variable in the existing code is confusing.

[wxiaoguang]

Yup, it is, and I also left some comments ....