Merge branch 'sb/pull-rebase-submodule'

"git pull --rebase --recurse-submodules" learns to rebase the branch in the submodules to an updated base. * sb/pull-rebase-submodule: builtin/fetch cleanup: always set default value for submodule recursing pull: optionally rebase submodules (remote submodule changes only) builtin/fetch: parse recurse-submodules-default at default options parsing builtin/fetch: factor submodule recurse parsing out to submodule config