Re: [WIP] Shift rev-list enumeration from upload-pack to pack-objects

> instead of using the internal revision walker and piping object refs
> to pack-objects this patch passes only the revs to pack-objects, which
> in turn handles both enumeration and packing.
> 
> Signed-off-by: Sam Vilain <sam@vilain.net>
> ---
>   Submitted on behalf of Nick in order to get wider feedback on this.
>   This version passes the test suite.
> 
>  upload-pack.c |   54 +++++++++++++++++++++++++++++++++++++++++++++---------
>  1 files changed, 45 insertions(+), 9 deletions(-)
> 
> diff --git a/upload-pack.c b/upload-pack.c
> index edc7861..7eda8fd 100644
> --- a/upload-pack.c
> +++ b/upload-pack.c
> @@ -155,13 +155,27 @@ static void create_pack_file(void)
>  	const char *argv[10];
>  	int arg = 0;
>  
> -	rev_list.proc = do_rev_list;
> -	/* .data is just a boolean: any non-NULL value will do */
> -	rev_list.data = create_full_pack ? &rev_list : NULL;
> -	if (start_async(&rev_list))
> -		die("git upload-pack: unable to fork git-rev-list");
> -
> -	argv[arg++] = "pack-objects";
> +	/* sending rev params to pack-objects directly is great, but unfortunately pack-objects 
> +	 * has no way of turning off thin pack generation.  this would be a relatively simple 
> +	 * addition, but as we also have to deal with shallow grafts and all it's simplest to 
> +	 * just resort to piping object refs.
> +	 */

> +	if (!use_thin_pack) {
> +		rev_list.proc = do_rev_list;
> +		/* .data is just a boolean: any non-NULL value will do */
> +		rev_list.data = create_full_pack ? &rev_list : NULL;
> +		if (start_async(&rev_list))
> +			die("git upload-pack: unable to fork git-rev-list");
> +		
> +		argv[arg++] = "pack-objects";
> +	} else {
> +		argv[arg++] = "pack-objects";
> +		argv[arg++] = "--revs";
> +		argv[arg++] = "--include-tag";