Fix traceback when nothing was added during unbundle
The changegroup and commit hook are now run only when
something is modified.
The correct number of changesets added is printed.
pushing to ../a
searching for changes
abort: unsynced remote changes!
(did you forget to sync? use push -f to force)
pulling from ../a
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files (+1 heads)
(run 'hg update' to get a working copy)
pushing to ../a
searching for changes
abort: push creates new remote branches!
(did you forget to merge? use push -f to force)
pushing to ../a
searching for changes
adding changesets
adding manifests
adding file changes
added 2 changesets with 1 changes to 1 files