gitea doesn't run with readonly git config

[kachick]

Stating form is executed, but starting will be rejected with frozen git config

> nix develop
> TAGS="bindata sqlite sqlite_unlock_notify" make build
> ./gitea web
2024/06/04 12:11:39 routers/common/db.go:23:InitDBEngine() [I] Beginning ORM engine initialization.
2024/06/04 12:11:39 routers/common/db.go:30:InitDBEngine() [I] ORM engine initialization attempt #1/10...
2024/06/04 12:11:39 ...s/install/install.go:594:SubmitInstall() [I] First-time run install finished!
2024/06/04 12:11:42 cmd/web.go:355:listen() [I] HTTP Listener: 0.0.0.0:3000 Closed
2024/06/04 12:11:42 cmd/web.go:111:showWebStartupMessage() [I] Gitea version: 1.23.0+dev-177-g433963e52c built with GNU Make 4.4.1, go1.22.2 : bindata, sqlite, sqlite_unlock_notify
2024/06/04 12:11:42 cmd/web.go:112:showWebStartupMessage() [I] * RunMode: prod
2024/06/04 12:11:42 cmd/web.go:113:showWebStartupMessage() [I] * AppPath: /home/kachick/repos/github.com/go-gitea/gitea/gitea
2024/06/04 12:11:42 cmd/web.go:114:showWebStartupMessage() [I] * WorkPath: /home/kachick/repos/github.com/go-gitea/gitea
2024/06/04 12:11:42 cmd/web.go:115:showWebStartupMessage() [I] * CustomPath: /home/kachick/repos/github.com/go-gitea/gitea/custom
2024/06/04 12:11:42 cmd/web.go:116:showWebStartupMessage() [I] * ConfigFile: /home/kachick/repos/github.com/go-gitea/gitea/custom/conf/app.ini
2024/06/04 12:11:42 cmd/web.go:117:showWebStartupMessage() [I] Prepare to run web server
2024/06/04 12:11:42 routers/init.go:73:mustInitCtx() [F] code.gitea.io/gitea/modules/git.InitFull(ctx) failed: failed to set git global config diff.algorithm, err: exit status 255 - error: could not lock config file /home/kachick/.config/git/config: Permission denied
 - error: could not lock config file /home/kachick/.config/git/config: Permission denied

Looks like same problem as go-gitea/gitea#28810

[kachick]

If I use NixOS and no develop versions, this module maybe useful

[kachick]

https://forgejo.org/

[kachick]

Part of GH-504?

[kachick]

See #850