Add exclude/maxdepth -n 1 flags

[brainstorm]

Hello pancake,

We are currently considering fsmon for high-throughput DNA sequencing @umccr but after trying other inotify-based systems, we found a common drawback: they all break since we have >200.000 directories being created on a regular basis (yes, the sad reality of DNA sequencer software we cannot easily circumvent, unfortunately).

Would it be much hassle to implement monitors that only go up to one level in the directory hierarchy so that the monitoring of new files goes faster? Pretty much all the other file monitoring systems either run out of memory or they just take a painfully long time to watch all the hierarchy (unnecessary in our use case).

Cheers!

/cc @reisingerf