The LastCommitCache code is a little complex and there is unnecessary
duplication between the gogit and nogogit variants.
This PR adds the LastCommitCache as a field to the git.Repository and
pre-creates it in the ReferencesGit helpers etc. There has been some
simplification and unification of the variant code.
Signed-off-by: Andrew Thornton <art27@cantab.net>
This module is merged from https://github.com/go-gitea/git which is a Go module to access Git through shell commands. Now it's a part of gitea's main repository for easier pull request.