Use gitrepo's clone and push when possible (#36093)

1 Move `IsRepositoryModelOrDirExist` and `CheckCreateRepository` to
service layer
2 Use `gitrepo.Pushxxx` instead of `git.Push` when possible
3 use `gitrepo.Clonexxx` instead of `gitrepo.Clone` when possible

services/repository/branch.go

@@ -385,8 +385,7 @@ func CreateNewBranchFromCommit(ctx context.Context, doer *user_model.User, repo
 		return err
 	}
 
-	if err := git.Push(ctx, repo.RepoPath(), git.PushOptions{
-		Remote: repo.RepoPath(),
+	if err := gitrepo.Push(ctx, repo, repo, git.PushOptions{
 		Branch: fmt.Sprintf("%s:%s%s", commitID, git.BranchPrefix, branchName),
 		Env:    repo_module.PushingEnvironment(doer, repo),
 	}); err != nil {