Follow up on scala3doc rename

Fixes https://github.com/sbt/sbt/issues/6307
Ref https://github.com/sbt/librarymanagement/pull/365
Ref https://github.com/lampepfl/dotty/pull/11289

This adds test using M4 nightly, which now uses artifact name
`scaladoc_3.0.0-M4` as oposed to `scala3doc_3.0.0-M3`.
The change in LM keeps the support for the old artifact name
for backward compatibility to build against 3.0.0-M1, -M2, and -M3.

project/Dependencies.scala

@@ -14,7 +14,7 @@ object Dependencies {
   // sbt modules
   private val ioVersion = nightlyVersion.getOrElse("1.5.0-M1")
   private val lmVersion =
-    sys.props.get("sbt.build.lm.version").orElse(nightlyVersion).getOrElse("1.5.0-M4")
+    sys.props.get("sbt.build.lm.version").orElse(nightlyVersion).getOrElse("1.5.0-M5")
   val zincVersion = nightlyVersion.getOrElse("1.5.0-M3")
 
   private val sbtIO = "org.scala-sbt" %% "io" % ioVersion

sbt/src/sbt-test/actions/doc-scala3/build.sbt

@@ -0,0 +1,7 @@
+ThisBuild / scalaVersion := "3.0.0-M4-bin-20210212-0273336-NIGHTLY"
+// ThisBuild / scalaVersion := "3.0.0-M3",
+
+lazy val root = (project in file("."))
+  .settings(
+    resolvers += Resolver.JCenterRepository
+  )

sbt/src/sbt-test/actions/doc-scala3/test

@@ -0,0 +1,17 @@
+> doc
+
+# there shouldn't be two api/ directories
+# see https://github.com/lampepfl/dotty/issues/11412
+$ exists target/scala-3.0.0-M4/api/api/index.html
+$ exists target/scala-3.0.0-M4/api/api/foo/A$.html
+$ exists target/scala-3.0.0-M4/api/api/foo.html
+
+> ++3.0.0-M3!
+> clean
+> doc
+
+# there shouldn't be two api/ directories
+# see https://github.com/lampepfl/dotty/issues/11412
+$ exists target/scala-3.0.0-M3/api/index.html
+$ exists target/scala-3.0.0-M3/api/api/foo/A$.html
+$ exists target/scala-3.0.0-M3/api/api/foo.html

sbt/src/sbt-test/actions/scala3-doc/build.sbt

@@ -1,5 +0,0 @@
-lazy val root = (project in file("."))
-  .settings(
-    scalaVersion := "3.0.0-M3",
-    resolvers += Resolver.JCenterRepository
-  )

sbt/src/sbt-test/actions/scala3-doc/test

@@ -1,4 +0,0 @@
-> doc
-$ exists target/scala-3.0.0-M3/api/index.html
-$ exists target/scala-3.0.0-M3/api/api/foo/A$.html
-$ exists target/scala-3.0.0-M3/api/api/foo.html