pack-objects: update size heuristucs.

We used to omit delta base candidates that is much bigger than
the target, but delta size does not grow when we delete more, so
that was not a very good heuristics.

Signed-off-by: Junio C Hamano <junkio@cox.net>

pack-objects.c

@@ -1032,12 +1032,6 @@ static int try_delta(struct unpacked *cur, struct unpacked *old, unsigned max_de
 		max_depth -= cur_entry->delta_limit;
 	}
 
-	size = cur_entry->size;
-	oldsize = old_entry->size;
-	sizediff = oldsize > size ? oldsize - size : size - oldsize;
-
-	if (size < 50)
-		return -1;
 	if (old_entry->depth >= max_depth)
 		return 0;
 
@@ -1048,9 +1042,12 @@ static int try_delta(struct unpacked *cur, struct unpacked *old, unsigned max_de
 	 * more space-efficient (deletes don't have to say _what_ they
 	 * delete).
 	 */
+	size = cur_entry->size;
 	max_size = size / 2 - 20;
 	if (cur_entry->delta)
 		max_size = cur_entry->delta_size-1;
+	oldsize = old_entry->size;
+	sizediff = oldsize < size ? size - oldsize : 0;
 	if (sizediff >= max_size)
 		return 0;
 	delta_buf = diff_delta(old->data, oldsize,
@@ -1109,6 +1106,9 @@ static void find_deltas(struct object_entry **list, int window, int depth)
 			 */
 			continue;
 
+		if (entry->size < 50)
+			continue;
+
 		free(n->data);
 		n->entry = entry;
 		n->data = read_sha1_file(entry->sha1, type, &size);