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.
unknown
acb14030fe0a tip
acb14030fe0a21b60322c440ad2d20cf7685a376 first
tip 1:b9154636be938d3d431e75a7c906504a079bfe07
first 0:acb14030fe0a21b60322c440ad2d20cf7685a376
b9154636be93 tip
M a
b9154636be93+ tip
acb14030fe0a+ first
acb14030fe0a21b60322c440ad2d20cf7685a376+ first
M a
c8edf04160c7 tip
c8edf04160c7+b9154636be93+ tip
M .hgtags