Point is, you may want to duplicate your set of collections, but not
duplicate all their objects.
Some notes:
* Am rather skeptical about the practice of using operator name to
define behavior of some common exec code. Imho, that should be a single
operator with an enum to refine its behavior (@cambpellbarton may also
have an opinion here?). Left it as-is for now, because this seems to be
used by other operators too in that code. :/
* @dfelinto, @pablovazquez, @billreynish am not so happy with current
names, but cannot find really good short ones either... Also, shouldn't
we move those into a dedicated `Duplicate` sub-menu?
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