packfile: pass source to prepare_pack()

When preparing a packfile we pass various pieces attached to the pack's
object database source via the `struct prepare_pack_data`. Refactor this
code to instead pass in the source directly. This reduces the number of
variables we need to pass and allows for a subsequent refactoring where
we start to prepare the pack via the source.

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

Author: pks-t

packfile.c

@@ -975,10 +975,8 @@ void for_each_file_in_pack_dir(const char *objdir,
 }
 
 struct prepare_pack_data {
-	struct repository *r;
+	struct odb_source *source;
 	struct string_list *garbage;
-	int local;
-	struct multi_pack_index *m;
 };
 
 static void prepare_pack(const char *full_name, size_t full_name_len,
@@ -988,10 +986,10 @@ static void prepare_pack(const char *full_name, size_t full_name_len,
 	size_t base_len = full_name_len;
 
 	if (strip_suffix_mem(full_name, &base_len, ".idx") &&
-	    !(data->m && midx_contains_pack(data->m, file_name))) {
+	    !(data->source->midx && midx_contains_pack(data->source->midx, file_name))) {
 		char *trimmed_path = xstrndup(full_name, full_name_len);
-		packfile_store_load_pack(data->r->objects->packfiles,
-					 trimmed_path, data->local);
+		packfile_store_load_pack(data->source->odb->packfiles,
+					 trimmed_path, data->source->local);
 		free(trimmed_path);
 	}
 
@@ -1020,10 +1018,8 @@ static void prepare_packed_git_one(struct odb_source *source)
 {
 	struct string_list garbage = STRING_LIST_INIT_DUP;
 	struct prepare_pack_data data = {
-		.m = source->midx,
-		.r = source->odb->repo,
+		.source = source,
 		.garbage = &garbage,
-		.local = source->local,
 	};
 
 	for_each_file_in_pack_dir(source->path, prepare_pack, &data);