Merge branch 'nd/clone-connectivity-shortcut' (early part) into maint

Cloning with "git clone --depth N" while fetch.fsckobjects (or transfer.fsckobjects) is set to true did not tell the cut-off points of the shallow history to the process that validates the objects and the history received, causing the validation to fail. * 'nd/clone-connectivity-shortcut' (early part): fetch-pack: prepare updated shallow file before fetching the pack clone: let the user know when check_everything_connected is run