-dit(bf(-x, --one-file-system)) This tells rsync not to cross filesystem
-boundaries when recursing. This is useful for transferring the
-contents of only one filesystem.
+dit(bf(-x, --one-file-system)) This tells rsync to avoid crossing a
+filesystem boundary when recursing. This does not limit the user's ability
+to specify items to copy from multiple filesystems, just rsync's recursion
+through the hierarchy of each directory that the user specified, and also
+the analogous recursion on the receiving side during deletion. Also keep
+in mind that rsync treats a "bind" mount to the same device as being on the
+same filesystem.
+
+If this option is repeated, rsync omits all mount-point directories from
+the copy. Otherwise, it includes an empty directory at each mount-point it
+encounters (using the attributes of the mounted directory because those of
+the underlying mount-point directory are inaccessible).
+
+If rsync has been told to collapse symlinks (via bf(--copy-links) or
+bf(--copy-unsafe-links)), a symlink to a directory on another device is
+treated like a mount-point. Symlinks to non-directories are unaffected
+by this option.
+
+dit(bf(--existing, --ignore-non-existing)) This tells rsync to skip
+updating files that do not exist yet on the destination. If this option is
+combined with the bf(--ignore-existing) option, no files will be updated
+(which can be useful if all you want to do is to delete missing files).