Move empty local repo logic for pull into findincoming
This fixes a silly attempt to pull a changegroup from an empty repo.
#!/bin/sh
hg init a
cd a
hg init b
echo x > b/x
echo '# should print nothing'
hg st
echo '# should print ? b/x'
hg st b/x
hg add b/x
echo '# should print A b/x'
hg st
echo '# should forget b/x'
hg forget
echo '# should print nothing'
hg st b