Merge branch 'sb/clone-shallow-passthru' into maint

Fix an unintended regression in v2.9 that breaks "clone --depth" that recurses down to submodules by forcing the submodules to also be cloned shallowly, which many server instances that host upstream of the submodules are not prepared for. * sb/clone-shallow-passthru: clone: do not let --depth imply --shallow-submodules