cli option > env var > config file

now target can be specified in config file.
renamed some function to use camelCase.

removed the old logger workaround when no object is used in fmt.

logger functions now support variable number of arguments.

now rsync should work if ssh key is present.

added short option support;
use real rsync command in Process.Start();

added unit test sub project.

fixed local.exclude typo

still missing many pieces and missing windows specific handling.