csum-file: stop depending on the_repository

There are multiple sites in "csum-file.c" where we use the global
`the_repository` variable, either explicitly or implicitly by using
`the_hash_algo`.

Refactor the code to stop using `the_repository` by adapting functions
to receive required data as parameters. Adapt callsites accordingly by
either using `the_repository->hash_algo`, or by using a context-provided
hash algorithm in case the subsystem already got rid of its dependency
on `the_repository`.

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

builtin/pack-objects.c

@@ -1311,7 +1311,8 @@ static void write_pack_file(void)
 		char *pack_tmp_name = NULL;
 
 		if (pack_to_stdout)
-			f = hashfd_throughput(1, "<stdout>", progress_state);
+			f = hashfd_throughput(the_repository->hash_algo, 1,
+					      "<stdout>", progress_state);
 		else
 			f = create_tmp_packfile(&pack_tmp_name);