Merge branch 'jk/leakfixes' into jk/sparse-leakfix

* jk/leakfixes:
  mv: replace src_dir with a strvec
  mv: factor out empty src_dir removal
  mv: move src_dir cleanup to end of cmd_mv()
  t-strvec: mark variable-arg helper with LAST_ARG_MUST_BE_NULL
  t-strvec: use va_end() to match va_start()