The Poll SCM trigger has two purposes:

1. Setting a cadence for polling SCM
2. Declaring that post commit hooks should be ignored

Currently if you want to ignore post commit hooks you are supposed to configure the trigger like so:

Now the issue here is that we are displaying a warning for a desired configuration. This leads users to think that they are doing something wrong.

As a consequence of this, we have had developers of other plugins add their own trigger implementations to control push trigger ignore behaviour (see GitHub plugin for an example)

What we really want is that the field validation should state that empty polling is OK when ignoring triggers:

But retain the field validation when either not ignoring hooks or ignoring hooks but invalid spec