# File lib/grit/git.rb, line 146
    def commit_from_sha(id)
      git_ruby_repo = GitRuby::Repository.new(self.git_dir)
      object = git_ruby_repo.get_object_by_sha1(id)

      if object.type == :commit
        id
      elsif object.type == :tag
        object.object
      else
        ''
      end
    end