Merge branch 'sb/test-cherry-pick-submodule-getting-in-a-way' into maint

The three-way merge performed by "git cherry-pick" was confused when a new submodule was added in the meantime, which has been fixed (or "papered over"). * sb/test-cherry-pick-submodule-getting-in-a-way: merge-recursive: handle addition of submodule on our side of history t/3512: demonstrate unrelated submodule/file conflict as cherry-pick failure