Add Jenkins "incrementals" binary repository

[alextu]

This fixes https://github.com/jenkinsci/gradle-jpi-plugin/issues/215. It just adds a new Maven repository named jenkinsIncrementals with default url of https://repo.jenkins-ci.org/incrementals. The url can be tweaked with the extension:

jenkinsPlugin {
    incrementalsRepoUrl = '...'
}

Note that this does not enforce a generated version to publish to the incrementals repository. To do so see https://github.com/jenkinsci/gradle-jpi-plugin/pull/218

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[sghill]

Thank you @alextu!

[alextu]

Thanks for reviewing and merging! (Next time, I can squash the commits before merging 😄 )

[alextu]

While writing the corresponding docs, I realized publish would publish to both https://repo.jenkins-ci.org/releases (or snapshot) and https://repo.jenkins-ci.org/incrementals and I wonder if it's a good idea, (I think the maven way is to explicity opt-in for such publication). Should we only configure jenkinsIncrementals repo according to a flag ?

[sghill]

Good point @alextu. I think we need to give folks a way to only publish to jenkinsIncrementals.

Using commons-lang3-api as an example, recent releases are in incrementals and releases, but many intermediate builds are published to incrementals.

[alextu]

Ok, I will work on a PR to address this

[sghill]

0.48.0 was released today with this change