t/helper/test-bitmap.c: add 'dump-hashes' mode

The pack-bitmap writer code is about to learn how to propagate values
from an existing hash-cache. To prepare, teach the test-bitmap helper to
dump the values from a bitmap's hash-cache extension in order to test
those changes.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

pack-bitmap.c

@@ -1742,6 +1742,33 @@ int test_bitmap_commits(struct repository *r)
 	return 0;
 }
 
+int test_bitmap_hashes(struct repository *r)
+{
+	struct bitmap_index *bitmap_git = prepare_bitmap_git(r);
+	struct object_id oid;
+	uint32_t i, index_pos;
+
+	if (!bitmap_git->hashes)
+		goto cleanup;
+
+	for (i = 0; i < bitmap_num_objects(bitmap_git); i++) {
+		if (bitmap_is_midx(bitmap_git))
+			index_pos = pack_pos_to_midx(bitmap_git->midx, i);
+		else
+			index_pos = pack_pos_to_index(bitmap_git->pack, i);
+
+		nth_bitmap_object_oid(bitmap_git, &oid, index_pos);
+
+		printf("%s %"PRIu32"\n",
+		       oid_to_hex(&oid), get_be32(bitmap_git->hashes + index_pos));
+	}
+
+cleanup:
+	free_bitmap_index(bitmap_git);
+
+	return 0;
+}
+
 int rebuild_bitmap(const uint32_t *reposition,
 		   struct ewah_bitmap *source,
 		   struct bitmap *dest)

pack-bitmap.h

@@ -52,6 +52,7 @@ void traverse_bitmap_commit_list(struct bitmap_index *,
 				 show_reachable_fn show_reachable);
 void test_bitmap_walk(struct rev_info *revs);
 int test_bitmap_commits(struct repository *r);
+int test_bitmap_hashes(struct repository *r);
 struct bitmap_index *prepare_bitmap_walk(struct rev_info *revs,
 					 struct list_objects_filter_options *filter,
 					 int filter_provided_objects);

t/helper/test-bitmap.c

@@ -7,6 +7,11 @@ static int bitmap_list_commits(void)
 	return test_bitmap_commits(the_repository);
 }
 
+static int bitmap_dump_hashes(void)
+{
+	return test_bitmap_hashes(the_repository);
+}
+
 int cmd__bitmap(int argc, const char **argv)
 {
 	setup_git_directory();
@@ -16,9 +21,12 @@ int cmd__bitmap(int argc, const char **argv)
 
 	if (!strcmp(argv[1], "list-commits"))
 		return bitmap_list_commits();
+	if (!strcmp(argv[1], "dump-hashes"))
+		return bitmap_dump_hashes();
 
 usage:
-	usage("\ttest-tool bitmap list-commits");
+	usage("\ttest-tool bitmap list-commits\n"
+	      "\ttest-tool bitmap dump-hashes");
 
 	return -1;
 }