Fix duplicate class entries in instrumentedJar that block plugin publishin (palantir#1714)

 Fix duplicate class entries in `instrumentedJar` that block plugin publishin

Author: crogoz

idea-plugin/build.gradle

@@ -75,3 +75,11 @@ dependencies {
 tasks.named("javadoc", Javadoc) {
     failOnError = false
 }
+
+// Prevent duplicate class entries in the instrumentedJar, which the JetBrains marketplace rejects.
+// The jar task's duplicatesStrategy is overridden from INHERIT to WARN. The instrumentedJar task
+// uses with(jarTask) to include the jar's CopySpec, so it picks up WARN and allows duplicates through.
+// Setting EXCLUDE here on the jar task propagates into instrumentedJar via that with(jarTask) call.
+tasks.named('jar') {
+    duplicatesStrategy = DuplicatesStrategy.EXCLUDE
+}