The `ctx.Repo.RefName` was used to be a "short name", it causes a lot of ambiguity. This PR does some refactoring and use `RefFullName` to replace the legacy `RefName`, and simplify RepoAssignment
Git Module
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.