Merge branch 'jc/maint-verify-objects-remove-pessimism'

The code to validate the history connectivity between old refs and new refs used by fetch and receive-pack, introduced in 1.7.8, was grossly inefficient and unnecessarily tried to re-validate integrity of individual objects. This essentially reverts that performance regression. * jc/maint-verify-objects-remove-pessimism: fetch/receive: remove over-pessimistic connectivity check