make mq play nicely with the branch cache - if no patches are applied, don't do anything different - if the cache includes valid data from one of the patch revisions, use the cache, but don't save anything new - if the cache has data from before the patch revisions only, save what the list of branches would be without the patch revisions

#!/bin/sh

hg init a
echo a > a/a
hg --cwd a ci -A -m a
hg clone a b
echo b > b/b
hg --cwd b ci -A -m b
chmod 100 a/.hg
hg --cwd b push ../a
chmod 700 a/.hg