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

modules/git/repo_branch.go

@@ -165,7 +165,7 @@ func (repo *Repository) AddRemote(name, url string, fetch bool) error {
 
 // RemoveRemote removes a remote from repository.
 func (repo *Repository) RemoveRemote(name string) error {
-	_, err := NewCommand("remote", "remove", name).RunInDir(repo.Path)
+	_, err := NewCommand("remote", "rm", name).RunInDir(repo.Path)
 	return err
 }