Move empty local repo logic for pull into findincoming
This fixes a silly attempt to pull a changegroup from an empty repo.
pulling from ../source
abort: pretxncommit hook exited with status 1
transaction abort!
rollback completed
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files
(run 'hg update' to get a working copy)
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
1 files, 2 changesets, 2 total revisions