[2.x] add no-op addDependencyTreePlugin shim for migration

main/src/main/scala/sbt/Defaults.scala

@@ -4747,6 +4747,13 @@ trait BuildExtra extends BuildCommon with DefExtra {
     Seq(compose(onLoad, add), compose(onUnload, remove))
   }
 
+  /**
+   * Adds dependency tree plugin.
+   */
+  @deprecated("dependencyTree is built into sbt 2.x; this is now a no-op", "2.0.0")
+  def addDependencyTreePlugin: Setting[Seq[ModuleID]] =
+    libraryDependencies ++= Nil
+
   /**
    * Adds Maven resolver plugin.
    */

sbt-app/src/sbt-test/project/add-dependency-tree-plugin-shim/build.sbt

@@ -0,0 +1,5 @@
+import sbtassembly.AssemblyPlugin.autoImport._
+
+assembly / assemblyJarName := "plugin-survived.jar"
+
+TaskKey[Unit]("check") := ()

sbt-app/src/sbt-test/project/add-dependency-tree-plugin-shim/project/plugins.sbt

@@ -0,0 +1,2 @@
+addDependencyTreePlugin
+addSbtPlugin("com.eed3si9n" % "sbt-assembly" % "2.3.1")

sbt-app/src/sbt-test/project/add-dependency-tree-plugin-shim/test

@@ -0,0 +1 @@
+> check