The current implementation of checkBranchName is highly inefficient
involving opening the repository, the listing all of the branch names
checking them individually before then using using opened repo to get
the tags.
This PR avoids this by simply walking the references from show-ref
instead of opening the repository (in the nogogit case).
Signed-off-by: Andrew Thornton <art27@cantab.net>
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
