progress: stop using the_repository

Stop using `the_repository` in the "progress" subsystem by passing in a
repository when initializing `struct progress`. Furthermore, store a
pointer to the repository in that struct so that we can pass it to the
trace2 API when logging information.

Adjust callers accordingly by using `the_repository`. While there may be
some callers that have a repository available in their context, this
trivial conversion allows for easier verification and bubbles up the use
of `the_repository` by one level.

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

walker.c

@@ -172,7 +172,8 @@ static int loop(struct walker *walker)
 	uint64_t nr = 0;
 
 	if (walker->get_progress)
-		progress = start_delayed_progress(_("Fetching objects"), 0);
+		progress = start_delayed_progress(the_repository,
+						  _("Fetching objects"), 0);
 
 	while (process_queue) {
 		struct object *obj = process_queue->item;