[BEE-37070] add inline documentation for build strategies

[ampuscas]

Add inline documentation for Build Strategies

Testing done

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[jglick]

The fake f:entry does not look right. You should not need to resort to tricks to have help for a standard form control. I think the problem here is that the original page used unnecessarily low-level controls. Better to use the higher-level f:repeatableHeteroProperty which groks databinding and should allow you to simply create a file with the conventional name, help-buildStrategies.html.

[jglick]

Sort of works. Gets messed up when you click the help next to an actual strategy like Skip initial build on first branch indexing, which I suspect is due to this facet still using a nonstandard control.

[jglick]

So, showing

branch-api-plugin/src/main/resources/jenkins/branch/BranchSource/help-buildStrategies.html

Lines 2 to 4 in 09d4261

	By default (i.e. when empty), everything except tags will be automatically built whenever discovered or changed.
	If you add at least one strategy then the defaults will be disabled and only the configured strategies will be
	applied.

[jglick]

Might not be possible to use f:repeatableHeteroProperty currently since it does not support an explicit descriptors attribute and

branch-api-plugin/src/main/java/jenkins/branch/BranchSource.java

Lines 177 to 178 in 09cb8ea

	public List<BranchBuildStrategyDescriptor> buildStrategiesDescriptors(
	@NonNull MultiBranchProject project, @NonNull SCMSourceDescriptor sourceDescriptor) {

requires a special calculation.