Is there an easy way to execute the dependencyInsight task for all projects in my multi-project build?
For example, say I have :core, :test, :web modules and I would like to see the version of spring-core used by each of them. Is there any way to do this without defining a new task that will run dependencyInsight on each of the subprojects?
This is difficult to do via the command line as you can only run the report per-project. You can however very easily get this information from a Build Scan.
It can simply achieved with a little trick I broadly described in my blog post some time ago.
It is just required to add:
subprojects {
task allDepInsight(type: DependencyInsightReportTask) << {}
}
to your project build configuration and call (for example):
gradle allDepInsight --configuration testRuntime --dependency org.slf4j:slf4j-simple
The task is automatically executed for all subprojects.
The same can be done for just displaying all dependencies in all subprojects - see this post.
Update: Just after sending my answer I spotted the last sentence in the original question… Please note however, If you don’t want to modify your project configuration the init script could be probably used instead.
I want to bump this and ask what is the status quo.
Is gradle able to run
./gradlew dependencyInsight --configuration testRuntimeClasspath --dependency jetty
through all my projects?
No, dependencies and dependencyInsight tasks are designed to be called on one specific project.
If you really need that and cannot use a build scan, you need an approach similar to what Marcin posted, just with a bit less bad-practices. 
(not using task(...), not using subprojects { ... }, not using << {}, …