Restore functionality for early gits (#7775) (#8476)

* Change tests to make it possible to run TestGit with 1.7.2

* Make merge run on 1.7.2

* Fix tracking and staging branch name problem

* Ensure that git 1.7.2 works on tests

* ensure that there is no chance for conflicts

* Fix-up missing merge issues

* Final rm

* Ensure LFS filters run on the tests

* Do not sign commits from temp repo

* Apply suggestions from code review

* Update modules/repofiles/temp_repo.go

models/repo.go

@@ -1063,7 +1063,7 @@ func CleanUpMigrateInfo(repo *Repository) (*Repository, error) {
 		}
 	}
 
-	_, err := git.NewCommand("remote", "remove", "origin").RunInDir(repoPath)
+	_, err := git.NewCommand("remote", "rm", "origin").RunInDir(repoPath)
 	if err != nil && !strings.HasPrefix(err.Error(), "exit status 128 - fatal: No such remote ") {
 		return repo, fmt.Errorf("CleanUpMigrateInfo: %v", err)
 	}