Backport #8901
In investigating #7947 it has become clear that the storage component of go-git repositories needs closing.
This PR adds this Close function and adds the Close functions as necessary.
In TransferOwnership the ctx.Repo.GitRepo is closed if it is open to help prevent the risk of multiple open files.
Fixes#7947
* 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
* Restore tracking fetch change
* Apply suggestions from code review
* Update modules/repofiles/temp_repo.go
