Merge branch 'tr/reset-checkout-patch'

Merge branch 'tr/reset-checkout-patch'

* tr/reset-checkout-patch:
  stash: simplify defaulting to "save" and reject unknown options
  Make test case number unique
  tests: disable interactive hunk selection tests if perl is not available
  DWIM 'git stash save -p' for 'git stash -p'
  Implement 'git stash save --patch'
  Implement 'git checkout --patch'
  Implement 'git reset --patch'
  builtin-add: refactor the meat of interactive_add()
  Add a small patch-mode testing library
  git-apply--interactive: Refactor patch mode code
  Make 'git stash -k' a short form for 'git stash save --keep-index'