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/doctor/misc.go

@@ -215,7 +215,7 @@ func checkCommitGraph(ctx context.Context, logger log.Logger, autofix bool) erro
 		if !isExist {
 			numNeedUpdate++
 			if autofix {
-				if err := git.WriteCommitGraph(ctx, repo.RepoPath()); err != nil {
+				if err := gitrepo.WriteCommitGraph(ctx, repo); err != nil {
 					logger.Error("Unable to write commit-graph in %s. Error: %v", repo.FullName(), err)
 					return err
 				}