Merge branch 'jt/fetch-tips-in-partial-clone'

"git fetch $repo $object" in a partial clone did not correctly
fetch the asked-for object that is referenced by an object in
promisor packfile, which has been fixed.

* jt/fetch-tips-in-partial-clone:
  fetch: in partial clone, check presence of targets
  connected: document connectivity in partial clones

diff --cc t/t5616-partial-clone.sh
Simple merge