gradle importer does not handle non-hierarchical project layouts

[afrische]

when importing a gradle project with a non-hierarchical project layout ( that is, a subproject outside of the root project ), mill will fail

Exception in thread "main" java.lang.IllegalArgumentException: requirement failed: ups must be zero, but it is 1 in ../gradle-subproject at scala.Predef$.require(Predef.scala:337) at os.RelPath.asSubPath(Path.scala:345) at os.BasePath.subRelativeTo(Path.scala:141) at os.BasePath.subRelativeTo$(Path.scala:115) at os.Path.subRelativeTo(Path.scala:567) at mill.main.gradle.GradleBuildGenMain$.$anonfun$5(GradleBuildGenMain.scala:79) at mill.main.buildgen.Tree$.recurse$2(Tree.scala:36) at mill.main.buildgen.Tree$.recurse$2$$anonfun$1(Tree.scala:37) at scala.collection.Iterator$$anon$9.next(Iterator.scala:584) at scala.collection.immutable.List.prependedAll(List.scala:153) at scala.collection.immutable.List$.from(List.scala:685) at scala.collection.immutable.List$.from(List.scala:682) at scala.collection.SeqFactory$Delegate.from(Factory.scala:306) at scala.collection.immutable.Seq$.from(Seq.scala:42) at scala.collection.IterableOnceOps.toSeq(IterableOnce.scala:1473) at scala.collection.IterableOnceOps.toSeq$(IterableOnce.scala:1473) at scala.collection.AbstractIterator.toSeq(Iterator.scala:1306) at mill.main.buildgen.Tree$.recurse$2(Tree.scala:37) at mill.main.buildgen.Tree$.from(Tree.scala:40) at mill.main.gradle.GradleBuildGenMain$.run(GradleBuildGenMain.scala:77) at mill.main.gradle.GradleBuildGenMain$.main(GradleBuildGenMain.scala:50) at mill.main.gradle.GradleBuildGenMain.main(GradleBuildGenMain.scala)

it can be provoked with the following settings.gradle

include('baz')
  include(['baz'])
  project(':baz').projectDir = file('../gradle-subproject')

i created a minimal reproducible example for your convenience at https://github.com/afrische/gradle-import-nonhierarchical