Add option for a separate idle event timeout

[jarruda]

The --fire-idle-event option uses a period of 110% of the latency period. Reference

I would like to be able to set a different period for the idle event that is not based on the latency.

Use case:
My application uses the latency option to debounce several changes made in quick succession, and would like to use the idle period to perform maintenance activities. The scale of these two operations are an order of magnitude apart (5s vs 60s). My application uses fswatch to sleep for the majority of the time and only wake on file changes. If the idle event fires at roughly the latency period, then fswatch provides almost no value for my use case (I don't need to know which files changed).

An acceptable solution:

• Add a switch to specify an optional idle timeout/period. This value would override the default value of 110% of the latency value.

[emcrisostomo]

Thanks for the comment @jarruda, I'll look into this.