the supplied source dir (or all mount points if the arg is omitted).
The excludes are appropriately anchored relative to the supplied dir,
and honor rsync's trailing-slash idiom.
- Allow spaces and a few other extra chars in file names.
- For safety, disallow any option that takes an arg. This should
be improved in the future because it blocks options such as
--block-size=N, but without this rule the user could specify
something like --files-from=FILE or --backup-dir=DIR and have
it affect files outside the desired SUBDIR restriction.
- Switched to SSH_CONNECTION from the deprecated SSH_CLIENT.
- Strip "::ffff:" from the start of an IP from SSH_CONNECTION.
