Copies the file designated by the non-wild pathname designator FROM
to the file designated by the non-wild pathname designator TO. The following
keyword parameters are supported:

* :if-exists
this can be either :supersede or :error (the default). If it is :error then
a source/target-target-already-exists-error will be signaled if the file designated
by the TO pathname already exists.

* :if-does-not-exist
this can be either :ignore or :error (the default). If it is :error then
a source/target-source-does-not-exist-error will be signaled if the FROM pathname
designator does not exist.