use String#<< instead of String#+ in Git#sh and Git#wild_sh
      Git#sh uses 8K buffers instead of 1K
      packing and unpacking uses String#<< instead of String#+
      avoid exists check when loading alternates
      fix relative alternates paths
      typo

rick (15):
      explicitly make the Grit data classes lazily loaded (instead of every single ruby object).  Also, add attr_writer(:lazy_source) for lazy objects
      git-notes backport from github
      backport zero-padding bugfix from github
      update history
      backport from github, attempt to load mime-types locally before loading rubygems
      add Grit::Repo#batch for getting multiple commits in a single native git call.
      update history
      extract Grit::Repo#parse_batch
      Index#commit takes options and can specify a custom committed date
      allow Index#commit to specify separate authors and committers with correct timezones for the timestamps
      update history
      set parent correctly from options passed to Grit::Index#commit
      fix regression with actor argument in Grit::Index#commit
      document rtomayko's perf enhancements
      fix regression in Grit::Index#commit