Merge branch 'jt/lazy-object-fetch-fix'

The code to backfill objects in lazily cloned repository did not
work correctly, which has been corrected.

* jt/lazy-object-fetch-fix:
  fetch-object: set exact_oid when fetching
  fetch-object: unify fetch_object[s] functions

diff --cc sha1-file.c
Simple merge

diff --cc t/t0410-partial-clone.sh
Simple merge

diff --cc unpack-trees.c
Simple merge