[PATCH 0/2] optimizing pack access on "read only" fetch repos

This is a repost from here:

  http://thread.gmane.org/gmane.comp.version-control.git/211176

which got no response initially. Basically the issue is that read-only
repos (e.g., a CI server) whose workflow is something like:

  git fetch $some_branch &&
  git checkout -f $some_branch &&
  make test

will never run git-gc, and will accumulate a bunch of small packs and
loose objects, leading to poor performance.

Patch 1 runs "gc --auto" on fetch, which I think is sane to do.

Patch 2 optimizes our pack dir re-scanning for fetch-pack (which, unlike
the rest of git, should expect to be missing lots of objects, since we
are deciding what to fetch).

I think 1 is a no-brainer. If your repo is packed, patch 2 matters less,
but it still seems like a sensible optimization to me.

  [1/2]: fetch: run gc --auto after fetching
  [2/2]: fetch-pack: avoid repeatedly re-scanning pack directory

-Peff