This program computes which packs in your repository are redundant. The output is suitable for piping to xargs rm if you are in the root of the repository.
git pack-redundant accepts a list of objects on standard input. Any objects given will be ignored when checking which packs are required. This makes the following command useful when wanting to remove packs which contain unreachable objects.
git fsck --full --unreachable | cut -d -f3 | \ git pack-redundant --all | xargs rm