Optional filter files

[Jacob Weber]

Is it possible to call rsync and tell it to use a filter file if it  
exists, but otherwise continue without errors?

If I pass "--filter=. .rsync-filter", it will fail if .rsync-filter  
doesn't exist.

I know you can pass "--filter=: /.rsync-filter" to search for filter  
files in each directory. That won't fail if there aren't any such  
files. But I'm only interested in one file at the root.

Thanks,
Jacob