index-pack: show progress while checking objects

When 'git index-pack' is run by 'git clone', its check_objects()
function usually doesn't take long enough to be a concern, but I just
run into a situation where it took about a minute or so: I
inadvertently put some memory pressure on my tiny laptop while cloning
linux.git, and then there was quite a long silence between the
"Resolving deltas" and "Checking connectivity" progress bars.

Show a progress bar during the loop of check_objects() to let the user
know that something is still going on.

Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/index-pack.c

@@ -219,8 +219,16 @@ static unsigned check_objects(void)
 	unsigned i, max, foreign_nr = 0;
 
 	max = get_max_object_index();
-	for (i = 0; i < max; i++)
+
+	if (verbose)
+		progress = start_delayed_progress(_("Checking objects"), max);
+
+	for (i = 0; i < max; i++) {
 		foreign_nr += check_object(get_indexed_object(i));
+		display_progress(progress, i + 1);
+	}
+
+	stop_progress(&progress);
 	return foreign_nr;
 }