With '-u', for a file /aaa/bbb/ccc enlisted for backup,
it will only get into backup if /rom/aaa/bbb/ccc does not
exist or /aaa/bbb/ccc is different from /rom/aaa/bbb/ccc.
It also works with '-c', but only effective for files touched
but not modified.
Signed-off-by: Luiz Angelo Daros de Luca <luizluca@gmail.com>
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