Make Jetty version configurable via command line for testing new version or snapshot

[olamy]

Related to discussion around this jetty/jetty.project#12882

[olamy]

@wilkinsona ping.

[wilkinsona]

As already discussed in the Jetty issue, I don’t think we should do this. Our build doesn’t need it and we could accidentally break it or remove it as it appears to be unneeded.

[olamy]

Sadly this will not really help the jetty project to test new release with spring projects :(

[wilkinsona]

We’re more than happy to help but I think there’s a better approach that will be more robust. Please see my latest comment in the Jetty issue.

[olamy]

Sure but if the dsl change again in the future our usage of the init script will fail again without any way for us to notice it.

[wilkinsona]

It's not a DSL change that caused your init script to fail. The problem was that it assumed that the dependency management plugin was being used. That used to be the case for Spring Framework's build but it has never been the case for Spring Boot's build. The approach that I am proposing makes no assumptions about plugins that have applied and makes use of standard Gradle APIs. As such, it should be robust. Should breaking changes be made to Gradle's API in the future, the init script will now fail noticeably rather than silently doing nothing due to a missing plugin as it does now.