Hello,

I'd like to clone a subtree with a repeating timestamp so that the
repeater is removed from the original subtree and a single shifted and
repeating clone is created.  I don't think this is currently possible
with org-clone-subtree-with-time-shift.  For example, running
org-clone-subtree-with-time-shift with 1 clone and a shift of +2d on

    * sub
    <2015-06-21 Sun +1w>

results in

    * sub
    <2015-06-21 Sun>
    * sub
    <2015-06-23 Tue>
    * sub
    <2015-06-25 Thu +1w>

This is inline with the docstring of org-clone-subtree-with-time-shift.
The one clone is the subtree in the middle, and the two flanking
subtrees are how a repeating timestamp is handled.

The attached patch allows the number of specified clones to be 0,
resulting in

    * sub
    <2015-06-21 Sun>
    * sub
    <2015-06-23 Tue +1w>

which is still consistent with the documented behavior.