Re: [PATCH v1 3/5] list-objects-filter: implement composite filters

> Allow combining filters such that only objects accepted by all filters
> are shown. The motivation for this is to allow getting directory
> listings without also fetching blobs. This can be done by combining
> blob:none with tree:<depth>. There are massive repositories that have
> larger-than-expected trees - even if you include only a single commit.
> 
> The current usage requires passing the filter to rev-list, or sending
> it over the wire, as:
> 
> 	combine:<FILTER1>+<FILTER2>

>   standard input when --stdin is used). <depth>=1 will include only the
>   tree and blobs which are referenced directly by a commit reachable from
>   <commit> or an explicitly-given object. <depth>=2 is like <depth>=1
>   while also including trees and blobs one more level removed from an
>   explicitly-given commit or tree.
> ++
> +The form '--filter=combine:<filter1>+<filter2>+...<filterN>' combines
> +several filters.

>                    Only objects which are accepted by every filter are
> +included. Filters are joined by '{plus}' and individual filters are %-encoded
> +(i.e. URL-encoded). Besides the '{plus}' and '%' characters, the following
> +characters are reserved and also must be encoded:
> +`~!@#$^&*()[]{}\;",<>?`+&#39;&#96;+ as well as all characters with ASCII code
> +&lt;= `0x20`, which includes space and newline.

> diff --git a/list-objects-filter.c b/list-objects-filter.c
> index 8e8616b9b8..b97277a46f 100644
> --- a/list-objects-filter.c
> +++ b/list-objects-filter.c
> @@ -453,34 +453,148 @@ static void filter_sparse_path__init(
>   
>   	ALLOC_GROW(d->array_frame, d->nr + 1, d->alloc);
>   	d->array_frame[d->nr].defval = 0; /* default to include */
>   	d->array_frame[d->nr].child_prov_omit = 0;
>   
>   	ctx->filter_fn = filter_sparse;
>   	ctx->free_fn = filter_sparse_free;
>   	ctx->data = d;
>   }
>   
> +struct filter_combine_data {
> +	/* sub[0] corresponds to lhs, sub[1] to rhs. */
> +	struct {
> +		struct filter_context ctx;
> +		struct oidset seen;
> +		struct object_id skip_tree;
> +		unsigned is_skipping_tree : 1;
> +	} sub[2];
> +
> +	struct oidset rhs_omits;
> +};
> +
> +static void add_all(struct oidset *dest, struct oidset *src) {
> +	struct oidset_iter iter;
> +	struct object_id *src_oid;
> +
> +	oidset_iter_init(src, &iter);
> +	while ((src_oid = oidset_iter_next(&iter)) != NULL)
> +		oidset_insert(dest, src_oid);
> +}
> +
> +static void filter_combine_free(void *filter_data)
> +{
> +	struct filter_combine_data *d = filter_data;
> +	int i;
> +
> +	/* Anything omitted by rhs should be added to the overall omits set. */
> +	if (d->sub[0].ctx.omits)
> +		add_all(d->sub[0].ctx.omits, d->sub[1].ctx.omits);
> +
> +	for (i = 0; i < 2; i++) {
> +		list_objects_filter__release(&d->sub[i].ctx);
> +		oidset_clear(&d->sub[i].seen);
> +	}
> +	oidset_clear(&d->rhs_omits);
> +	free(d);
> +}
> +
> +static int should_delegate(enum list_objects_filter_situation filter_situation,
> +			   struct object *obj,
> +			   struct filter_combine_data *d,
> +			   int side)
> +{
> +	if (!d->sub[side].is_skipping_tree)
> +		return 1;
> +	if (filter_situation == LOFS_END_TREE &&
> +		oideq(&obj->oid, &d->sub[side].skip_tree)) {
> +		d->sub[side].is_skipping_tree = 0;
> +		return 1;
> +	}
> +	return 0;
> +}
> +
> +static enum list_objects_filter_result filter_combine(
> +	struct repository *r,
> +	enum list_objects_filter_situation filter_situation,
> +	struct object *obj,
> +	const char *pathname,
> +	const char *filename,
> +	struct filter_context *ctx)
> +{
> +	struct filter_combine_data *d = ctx->data;
> +	enum list_objects_filter_result result[2];
> +	enum list_objects_filter_result combined_result = LOFR_ZERO;
> +	int i;
> +
> +	for (i = 0; i < 2; i++) {
> +		if (oidset_contains(&d->sub[i].seen, &obj->oid) ||
> +			!should_delegate(filter_situation, obj, d, i)) {

> +			result[i] = LOFR_ZERO;
> +			continue;
> +		}
> +
> +		result[i] = d->sub[i].ctx.filter_fn(
> +			r, filter_situation, obj, pathname, filename,
> +			&d->sub[i].ctx);
> +
> +		if (result[i] & LOFR_MARK_SEEN)
> +			oidset_insert(&d->sub[i].seen, &obj->oid);

> +		}
> +	}
> +
> +	if ((result[0] & LOFR_DO_SHOW) && (result[1] & LOFR_DO_SHOW))
> +		combined_result |= LOFR_DO_SHOW;
> +	if (d->sub[0].is_skipping_tree && d->sub[1].is_skipping_tree)
> +		combined_result |= LOFR_SKIP_TREE;