[PATCH] fix bug in read-cache.c which loses files when merging a tree

I noticed this when I tried a non-trivial scsi merge and checked the
results against BK.  The problem is that remove_entry_at() actually
decrements active_nr, so decrementing it in add_cache_entry() before
calling remove_entry_at() is a double decrement (hence we lose cache
entries at the end).

read-cache.c

@@ -402,7 +402,6 @@ int add_cache_entry(struct cache_entry *ce, int ok_to_add)
 	if (pos < active_nr && ce_stage(ce) == 0) {
 		while (same_name(active_cache[pos], ce)) {
 			ok_to_add = 1;
-			active_nr--;
 			if (!remove_entry_at(pos))
 				break;
 		}