Fix ./mill init unpack path (#5195)

`InitModule#init` assumes that zip file name is the same as the path to
the content inside the zip, which was broken recently in #5147. This PR
makes it consistent again by computing the name once and using it both
in naming the zip and in naming the enclosing folder of its contents

Author: lihaoyi

.mill-jvm-version

@@ -1 +1 @@
-zulu:17.0.14
+zulu:17.0.4

dist/package.mill

@@ -221,14 +221,15 @@ object `package` extends MillJavaModule with DistModule {
     prepareBootstrapLauncher(millBootstrapBat().path, Task.dest, build.millVersion(), "mill.bat")
   }
 
-  def examplePathsWithArtifactName: Task[Seq[(PathRef, String)]] = Task.Input {
-    for {
-      exampleMod <- build.example.exampleModules
-      path = exampleMod.moduleDir
-    } yield {
-      val example = path.subRelativeTo(Task.workspace)
+  def examplePathsWithArtifactName0: Task[Seq[PathRef]] = Task.Input {
+    for (exampleMod <- build.example.exampleModules) yield PathRef(exampleMod.moduleDir)
+  }
+
+  def examplePathsWithArtifactName = Task {
+    for (pr <- examplePathsWithArtifactName0()) yield {
+      val example = pr.path.subRelativeTo(Task.workspace)
       val artifactName = example.segments.mkString("-")
-      (PathRef(path), artifactName)
+      (pr, s"${build.dist.artifactFileNamePrefix()}-$artifactName")
     }
   }
 

libs/init/package.mill

@@ -19,7 +19,7 @@ object `package` extends MillPublishScalaModule {
     val data: Seq[(os.SubPath, String)] =
       build.dist.examplePathsWithArtifactName().map { case (pathRef, str) =>
         val downloadUrl =
-          s"${build.millDownloadUrl()}/${build.dist.artifactFileNamePrefix()}-$str.zip"
+          s"${build.millDownloadUrl()}/$str.zip"
         val subPath = pathRef.path.subRelativeTo(Task.workspace / "example")
         (subPath, downloadUrl)
       }
@@ -118,8 +118,7 @@ object `package` extends MillPublishScalaModule {
     )
 
     // An `sbt` plugin is built with Scala 2.12. See https://www.scala-sbt.org/1.x/docs/Plugins.html#Creating+an+auto+plugin.
-    object models
-        extends Cross[ModelsModule](Deps.sbtScalaVersion212, Deps.scalaVersion)
+    object models extends Cross[ModelsModule](Deps.sbtScalaVersion212, Deps.scalaVersion)
     trait ModelsModule extends MillPublishCrossScalaModule {
       // def moduleDeps = Seq(buildgen.tree())
       def mvnDeps = Seq(Deps.upickle)