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>
---
 pack-bitmap.c                      | 41 +++++++++++++++++++++++++++---
 t/t6113-rev-list-bitmap-filters.sh |  7 +++++
 2 files changed, 44 insertions(+), 4 deletions(-)

diff --git a/pack-bitmap.c b/pack-bitmap.c
index cd3f5c433e..4385f15828 100644
--- a/pack-bitmap.c
+++ b/pack-bitmap.c
@@ -926,6 +926,29 @@ static void filter_bitmap_object_type(struct bitmap_index *bitmap_git,
 		filter_bitmap_exclude_type(bitmap_git, tip_objects, to_filter, OBJ_BLOB);
 }
 
+static int filter_supported(struct list_objects_filter_options *filter)
+{
+	int i;
+
+	switch (filter->choice) {
+	case LOFC_BLOB_NONE:
+	case LOFC_BLOB_LIMIT:
+	case LOFC_OBJECT_TYPE:
+		return 1;
+	case LOFC_TREE_DEPTH:
+		if (filter->tree_exclude_depth == 0)
+			return 1;
+		return 0;
+	case LOFC_COMBINE:
+		for (i = 0; i < filter->sub_nr; i++)
+			if (!filter_supported(&filter->sub[i]))
+				return 0;
+		return 1;
+	default:
+		return 0;
+	}
+}
+
 static int filter_bitmap(struct bitmap_index *bitmap_git,
 			 struct object_list *tip_objects,
 			 struct bitmap *to_filter,
@@ -933,6 +956,8 @@ static int filter_bitmap(struct bitmap_index *bitmap_git,
 {
 	if (!filter || filter->choice == LOFC_DISABLED)
 		return 0;
+	if (!filter_supported(filter))
+		return -1;
 
 	if (filter->choice == LOFC_BLOB_NONE) {
 		if (bitmap_git)
@@ -949,8 +974,7 @@ static int filter_bitmap(struct bitmap_index *bitmap_git,
 		return 0;
 	}
 
-	if (filter->choice == LOFC_TREE_DEPTH &&
-	    filter->tree_exclude_depth == 0) {
+	if (filter->choice == LOFC_TREE_DEPTH) {
 		if (bitmap_git)
 			filter_bitmap_tree_depth(bitmap_git, tip_objects,
 						 to_filter,
@@ -966,8 +990,17 @@ static int filter_bitmap(struct bitmap_index *bitmap_git,
 		return 0;
 	}
 
-	/* filter choice not handled */
-	return -1;
+	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;
+	}
+
+	BUG("unsupported filter choice");
 }
 
 static int can_filter_bitmap(struct list_objects_filter_options *filter)
diff --git a/t/t6113-rev-list-bitmap-filters.sh b/t/t6113-rev-list-bitmap-filters.sh
index fb66735ac8..cb9db7df6f 100755
--- a/t/t6113-rev-list-bitmap-filters.sh
+++ b/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
-- 
2.31.1