copy-clear shelf-type? shelf-name to shelf-name

Copies the entire contents of one shelf to another of the same type (counter, switch or stream), then clears the source shelf of all items. This action replaces the current contents of the destination shelf, and closes all streams on it. Open streams in the source shelf will still be open in the destination shelf.

Unlike the copy action, copy-clear requires that the source shelf be of variable type.

The destination shelf must be either of variable size or the same size as the source shelf. If it is variable with a maximum size, the maximum size must be greater than the size of the source shelf.