bundle: quick fix to ludicrous performance penalty
We tried a
hg bundle --base ':(tip^)' --rev 'all()' on a large repository and
it spent 3 minutes on this 2 list comprehensions. This change remove this cost.
There are still a lot of low hanging fruits as the command still take 30 seconds. However this is a trivial patch with a massive speedup so I'll just sent it.