pack-bitmap: implement combined filter

When the user has multiple objects filters specified, then this is
internally represented by having a "combined" filter. These combined
filters aren't yet supported by bitmap indices and can thus not be
accelerated.

Fix this by implementing support for these combined filters. The
implementation is quite trivial: when there's a combined filter, we
simply recurse into `filter_bitmap()` for all of the sub-filters.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

pack-bitmap.c

@@ -966,6 +966,16 @@ static int filter_bitmap(struct bitmap_index *bitmap_git,
 		return 0;
 	}
 
+	if (filter->choice == LOFC_COMBINE) {
+		int i;
+		for (i = 0; i < filter->sub_nr; i++) {
+			if (filter_bitmap(bitmap_git, tip_objects, to_filter,
+					  &filter->sub[i]) < 0)
+				return -1;
+		}
+		return 0;
+	}
+
 	/* filter choice not handled */
 	return -1;
 }

t/t6113-rev-list-bitmap-filters.sh

@@ -98,4 +98,11 @@ test_expect_success 'object:type filter' '
 	test_bitmap_traversal expect actual
 '
 
+test_expect_success 'combine filter' '
+	git rev-list --objects --filter=blob:limit=1000 --filter=object:type=blob tag >expect &&
+	git rev-list --use-bitmap-index \
+		     --objects --filter=blob:limit=1000 --filter=object:type=blob tag >actual &&
+	test_bitmap_traversal expect actual
+'
+
 test_done