Merge branch 'js/reflog-delete'

* js/reflog-delete:
  t3903-stash.sh: Add tests for new stash commands drop and pop
  git-reflog.txt: Document new commands --updateref and --rewrite
  t3903-stash.sh: Add missing '&&' to body of testcase
  git-stash: add new 'pop' subcommand
  git-stash: add new 'drop' subcommand
  git-reflog: add option --updateref to write the last reflog sha1 into the ref
  refs.c: make close_ref() and commit_ref() non-static
  git-reflog: add option --rewrite to update reflog entries while expiring
  reflog-delete: parse standard reflog options
  builtin-reflog.c: fix typo that accesses an unset variable
  Teach "git reflog" a subcommand to delete single entries