Merge branch 'wc/add-i'

Merge branch 'wc/add-i'

* wc/add-i:
  git-add -i: add help text for list-and-choose UI
  add -i: allow prefix highlighting for "Add untracked" as well.
  Highlight keyboard shortcuts in git-add--interactive
  Document all help keys in "git add -i" patch mode.
  Add "--patch" option to git-add--interactive
  add -i: Fix running from a subdirectory
  builtin-add: fix command line building to call interactive
  git-add -i: allow multiple selection in patch subcommand
  Add path-limiting to git-add--interactive
  Teach builtin-add to pass multiple paths to git-add--interactive