mirror: command should no-op if used repeatedly!
mirror: command should no-op if used repeatedly!

The semantics of this are good for CA warehouses; not so great for single file targets, as is typical.

Signed-off-by: Eric Myhre <2346ad27d7568ba9896f1b7da6b5991251debdf2@exultant.us>

polydawn/rio,polydawn/rio