HEAD is not set to alternative default brach when using a template

[kb173]

• Gitea version (or commit ref): 1.14.0+dev-290-gb1cf7f4df built with GNU Make 4.3, go1.15.5 : bindata, timetzdata, sqlite, sqlite_unlock_notify
• Git version: 2.26.2
• Operating system: 18.04.5 LTS

I am running Gitea using Docker, using the (slightly modified) docker-compose.yaml.

• Database (use [x]):
  • PostgreSQL
  • MySQL
  • MSSQL
  • SQLite
• Can you reproduce the bug at https://try.gitea.io:
  • Yes (on https://gitea.com/, as I tried reproducing there before noticing this link: https://gitea.com/kb173/main-bug)
  • No

Description

I created a template repository whose default branch is named "main" instead of "master". When I create a new repository from this template, ticking "Git Content (Default Branch)", the HEAD is set incorrectly on the server:

When cloning, I get the notice "warning: remote HEAD refers to nonexistent ref, unable to checkout.". I get placed in the non-existent master branch and I need to manually checkout the main branch in order to access the files in the repository.

Upon inspection of the HEAD on the remote (in the Gitea repository folder on the server, via SSH), I see that the HEAD is set wrongly. It is ref: refs/heads/master, but it should be ref: refs/heads/main. Manually editing this solves the issue for this repository.

Note that this is not the case in the template repository, only in the one instanced from this template.

I reproduced the issue in https://gitea.com/kb173/main-bug, which is instanced from the template https://gitea.com/kb173/template-default-main. As you can see, the web-UI correctly shows "main" as the only branch, but when cloning, the aforementioned warning occurs.

Seems to be related to #7601. While that is indeed fixed when creating a new repository from scratch, the problem seems to persist with repositories from templates.