Merge branch 'jt/submodule-pull-recurse-rebase'

"git pull -recurse-submodules --rebase", when the submodule repository's history did not have anything common between ours and the upstream's, failed to execute. We need to fetch from them to continue even in such a case. * jt/submodule-pull-recurse-rebase: submodule: do not pass null OID to setup_revisions