[PATCH 0/4] a few small unused-parameter fixes

These ones are not annotations of unused parameters, but rather code changes that (I hope) make the world a better place while also silencing -Wunused-parameters.

I've been trying to bubble these up to the front of my series of UNUSED annotations. I _thought_ I had got all of them, but I think a few of these are new, and some are ones that just got lost in the shuffle of earlier series.

  [1/4]: test-submodule: inline resolve_relative_url() function
  [2/4]: multi-pack-index: avoid writing to global in option callback
  [3/4]: commit: avoid writing to global in option callback
  [4/4]: attr: convert DEBUG_ATTR to use trace API

 attr.c                     | 38 +++++++++++++++++---------------------
 builtin/commit.c           |  4 ++--
 builtin/multi-pack-index.c |  7 ++++---
 t/helper/test-submodule.c  | 22 ++++++++--------------
 4 files changed, 31 insertions(+), 40 deletions(-)

-Peff