Add support for sha256 repositories (#23894)

Currently only SHA1 repositories are supported by Gitea. This adds
support for alternate SHA256 with the additional aim of easier support
for additional hash types in the future.

Fixes: #13794
Limited by: https://github.com/go-git/go-git/issues/899
Depend on: #28138

<img width="776" alt="图片" src="https://github.com/go-gitea/gitea/assets/81045/5448c9a7-608e-4341-a149-5dd0069c9447">

---------

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: 6543 <6543@obermui.de>

routers/api/v1/repo/repo.go

@@ -253,7 +253,7 @@ func CreateUserRepo(ctx *context.APIContext, owner *user_model.User, opt api.Cre
 		DefaultBranch:    opt.DefaultBranch,
 		TrustModel:       repo_model.ToTrustModel(opt.TrustModel),
 		IsTemplate:       opt.Template,
-		ObjectFormatName: git.Sha1ObjectFormat.Name(),
+		ObjectFormatName: opt.ObjectFormatName,
 	})
 	if err != nil {
 		if repo_model.IsErrRepoAlreadyExist(err) {