Re: [PATCH 3/8] builtin/maintenance: introduce "geometric-repack" task

> Introduce a new "geometric-repack" task. This task uses our geometric
> repack infrastructure as provided by git-repack(1) itself, which is a
> strategy that especially hosting providers tend to use to amortize the
> costs of repacking objects.
> 
> There is one issue though with geometric repacks, namely that they
> unconditionally pack all loose objects, regardless of whether or not
> they are reachable. This is done because it means that we can completely
> skip the reachability step, which significantly speeds up the operation.
> But it has the big downside that we are unable to expire objects over
> time.
> 
> To address this issue we thus use a split strategy in this new task:
> whenever a geometric repack would merge together all packs, we instead
> do an all-into-one repack. By default, these all-into-one repacks have
> cruft packs enabled, so unreachable objects would now be written into
> their own pack. Consequently, they won't be soaked up during geometric
> repacking anymore and can be expired with the next full repack, assuming
> that their expiry date has surpassed.

> @@ -1566,6 +1568,101 @@ static int maintenance_task_incremental_repack(struct maintenance_run_opts *opts
>  	return 0;
>  }
>  
> +static int maintenance_task_geometric_repack(struct maintenance_run_opts *opts,
> +					     struct gc_config *cfg)
> +{
> +	struct pack_geometry geometry = {
> +		.split_factor = 2,
> +	};
> +	struct pack_objects_args po_args = {
> +		.local = 1,
> +	};
> +	struct existing_packs existing_packs = EXISTING_PACKS_INIT;
> +	struct string_list kept_packs = STRING_LIST_INIT_DUP;
> +	struct child_process child = CHILD_PROCESS_INIT;
> +	int ret;
> +
> +	existing_packs.repo = the_repository;
> +	existing_packs_collect(&existing_packs, &kept_packs);
> +	pack_geometry_init(&geometry, &existing_packs, &po_args);
> +	pack_geometry_split(&geometry);
> +
> +	child.git_cmd = 1;
> +
> +	strvec_pushl(&child.args, "repack", "-d", "-l", NULL);
> +	if (geometry.split < geometry.pack_nr)
> +		strvec_push(&child.args, "--geometric=2");
> +	else
> +		add_repack_all_option(cfg, NULL, &child.args);

> @@ -1608,6 +1705,11 @@ static const struct maintenance_task tasks[] = {
>  		.background = maintenance_task_incremental_repack,
>  		.auto_condition = incremental_repack_auto_condition,
>  	},
> +	[TASK_GEOMETRIC_REPACK] = {
> +		.name = "geometric-repack",
> +		.background = maintenance_task_geometric_repack,
> +		.auto_condition = geometric_repack_auto_condition,
> +	},