Pointing to https://$IDP_URL/status in the browser will show you...
Or if you unpack the war file and have a look in WEB-INF/lib. There
should be file called shibboleth-identityprovider-<VERSION>.jar
If you don't trust that, there is a standalone app
edu.internet2.middleware.shibboleth.idp.Version, which can be run as
java -cp shibboleth-identityprovider-<VERSION>.jar
edu.internet2.middleware.shibboleth.idp.Version
I think this just grabs the info from the jar file's manifest
/gav