Merge branch 'master' into next

* master:
  3% tighter packs for free
  Rewrite synopsis to clarify the two primary uses of git-checkout.
  Fix minor typo.
  Reference git-commit-tree for env vars.
  Clarify git-rebase example commands.
  Document the default source of template files.
  Call out the two different uses of git-branch and fix a typo.
  Add git-show reference