Update delta compression message to be less misleading

In the case of a small repository, pack-objects is smart enough to not
start more threads than necessary. However, the output to the user always
reports the value of the pack.threads configuration and not the real
number of threads to be used.

Signed-off-by: Dan McGee <dpmcgee@gmail.com>
Acked-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-pack-objects.c

@@ -1612,7 +1612,7 @@ static void ll_find_deltas(struct object_entry **list, unsigned list_size,
 		return;
 	}
 	if (progress > pack_to_stdout)
-		fprintf(stderr, "Delta compression using %d threads.\n",
+		fprintf(stderr, "Delta compression using up to %d threads.\n",
 				delta_search_threads);
 
 	/* Partition the work amongst work threads. */