# src, dest are strings
# on_dir, on_file are Procs

def copy_transform src, dest, on_dir, on_file
    # walking src recursively
    # call the appropriate block to make the transformation happen
    # use the the result to create a directory of file
end

Net::SSH.start(<host>, <usr>) do |ssh|
    # redirect all the write and/or read operations like:
    # mkdir, cp, mv, rm
    # to the ssh-object given to the block

    copy_transform 'src', 'dest', proc1, proc2

    # restore every stream
end