tests/test-nested-repo

Fix income/pull with bundle and -R (issue 820).

Uses ui.setconfig() to tell bundlerepo where the main repo is. This is
needed for when the --repository option is used.

Adds tests to test-bundle and a new test script
test-mq-pull-from-bundle, which plays out the situation that initially
made me detect this bug

(hg -R .hg/patches pull ../bundle.hg).

#!/bin/sh

hg init a
cd a
hg init b
echo x > b/x

echo '# should print nothing'
hg add b
hg st

echo '# should fail'
hg st b/x
hg add b/x

echo '# should fail'
hg add b b/x
hg st

echo '# should arguably print nothing'
hg st b

echo a > a
hg ci -Ama a

echo '# should fail'
hg mv a b
hg st