Fix performance regression in addremove command. When I rewrote addremove, I lazily put a call to repo.changes in, which was unnecessary and slow. This is a new rewrite, preserving the file name behaviour, but replacing the call to repo.changes with a walk, which is much cheaper, and avoids calls to os.stat on all but files that have probably been deleted.

#!/bin/bash

set -x
mkdir a
cd a
hg init
echo a > a
hg add a
hg commit -m test -d '0 0'

# Default operation
hg clone . ../b
cd ../b
cat a
hg verify

# No update
hg clone -U . ../c
cd ../c
cat a
hg verify

# Default destination
mkdir ../d
cd ../d
hg clone ../a
cd a
hg cat a