Revert "pack-objects: only throw away data during memory pressure"

This reverts commit 9c2174350c.

Nico analyzed and found out that this does not really help, and
I agree with it.

By the time this gets into action and data is actively thrown
away, performance simply goes down the drain due to the data
constantly being reloaded over and over and over and over and
over and over again, to the point of virtually making no
relative progress at all.  The previous behavior of enforcing
the memory limit by dynamically shrinking the window size at
least had the effect of allowing some kind of progress, even if
the end result wouldn't be optimal.

And that's the whole point behind this memory limiting feature:
allowing some progress to be made when resources are too limited
to let the repack go unbounded.

builtin-pack-objects.c

@@ -1464,7 +1464,7 @@ static unsigned int check_delta_limit(struct object_entry *me, unsigned int n)
 	return m;
 }
 
-static unsigned long free_unpacked_data(struct unpacked *n)
+static unsigned long free_unpacked(struct unpacked *n)
 {
 	unsigned long freed_mem = sizeof_delta_index(n->index);
 	free_delta_index(n->index);
@@ -1474,12 +1474,6 @@ static unsigned long free_unpacked_data(struct unpacked *n)
 		free(n->data);
 		n->data = NULL;
 	}
-	return freed_mem;
-}
-
-static unsigned long free_unpacked(struct unpacked *n)
-{
-	unsigned long freed_mem = free_unpacked_data(n);
 	n->entry = NULL;
 	n->depth = 0;
 	return freed_mem;
@@ -1520,7 +1514,7 @@ static void find_deltas(struct object_entry **list, unsigned *list_size,
 		       mem_usage > window_memory_limit &&
 		       count > 1) {
 			uint32_t tail = (idx + window - count) % window;
-			mem_usage -= free_unpacked_data(array + tail);
+			mem_usage -= free_unpacked(array + tail);
 			count--;
 		}
 
@@ -1553,9 +1547,6 @@ static void find_deltas(struct object_entry **list, unsigned *list_size,
 			if (!m->entry)
 				break;
 			ret = try_delta(n, m, max_depth, &mem_usage);
-			if (window_memory_limit &&
-			    mem_usage > window_memory_limit)
-				mem_usage -= free_unpacked_data(m);
 			if (ret < 0)
 				break;
 			else if (ret > 0)