JENKINS-67725 - Extending BranchBuildStrategies to allow setting last revision built + access to SCMEvent

[carpnick]

See JENKINS-67725 for more context.

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• [x] Please describe what you did
• [x] Link to relevant issues in GitHub or Jira
• [x] Link to relevant pull requests, esp. upstream and downstream changes
• [x] Ensure you have provided tests - that demonstrates feature works or fixes the issue

The basic use case:

• How do we enable the folks to "save" the first commit ID found, and only build everything after that. This update allows us to implement a BranchBuildStrategy to do that. Without this change we are not handed the right pieces to implement that use case.

Discussion

• As written this will always evaluate to true even if a BuildStrategy keeps responding, do not build. The next time a branch indexing comes in, it will evaluate to true since it did not build. This feels like a design flaw. As a plugin author I am telling you to not build it. As a Jenkins Admin I am telling you not to build it. But you are repeatedly trying to build it if I turn on branch indexing.
• As I see it we have 2 options
  • We extend BranchBuildStrategy and add another optional method that allows a plugin author to own if you can update the last built hash
  • We create a whole new extension point to give a plugin author the ability to define what changesDetected means.

What is in the PR

• Added a new extension method(optional) for plugin authors can choose to update last built revision or not. Default is false which is current behavior
• Added integration of new method into MultiBranchProject to evaluate if it should update lastbuiltrevision on disk if told not to build.
• Also added SCMEvent to the extension methods. Allows plugin authors to use properties to determine if we should build the artifact. The specific property I am looking for is timestamp. If I create a plugin that requires only building forward(from now) I need to know when the event was generated. This gives me that ability.

Please review at your convenience. This is ready.

[carpnick]

Could I get a review @jtnord and/or @rsandell ?

[carpnick]

Any kind of review would be appreciated... @timja or @car-roll

[carpnick]

I would also expect at least one downstream PR to demonstrate this new API.

ref: https://www.jenkins.io/doc/developer/extensions/branch-api/#branchbuildstrategy

Fair comment - I will either do a PR in one of the plugins that exists and/or create a plugin and link it here.