bump Scala 3 to 3.0.0-RC2; add version policy. fixes #150

Author: Sciss

Diff for: .travis.yml

@@ -8,7 +8,7 @@ scala:
   - 2.11.12
   - 2.12.11
   - 2.13.3
-  - 3.0.0-RC1
+  - 3.0.0-RC2
 
 env:
   - ADOPTOPENJDK=8

Diff for: build.sbt

@@ -1,4 +1,9 @@
-lazy val scalaTestVersion = "3.2.4"
+lazy val scalaTestVersion = "3.2.7"
+
+// We use <epoch>.<major>.<minor> like 99% of Scala libraries.
+// Versions are binary compatible within x.y.* but not within x.*.*
+ThisBuild / versionScheme := Some("pvp")
+ThisBuild / versionPolicyIntention := Compatibility.None  // 3.0.0
 
 lazy val commonSettings = Seq(
   scalacOptions     ++= Seq("-deprecation", "-feature"),

Diff for: build.sh

@@ -51,4 +51,4 @@ export CI_SNAPSHOT_RELEASE="${projectPrefix}publish"
 # for now, until we're confident in the new release scripts, just close the staging repo.
 export CI_SONATYPE_RELEASE="; sonatypePrepare; sonatypeBundleUpload; sonatypeClose"
 
-sbt clean ${projectPrefix}test ${projectPrefix}publishLocal $releaseTask
+sbt clean ${projectPrefix}test ${projectPrefix}versionPolicyCheck ${projectPrefix}publishLocal $releaseTask

Diff for: project/build.properties

@@ -1 +1 @@
-sbt.version=1.4.7
+sbt.version=1.4.9

Diff for: project/plugins.sbt

@@ -1,2 +1,3 @@
-addSbtPlugin("org.scala-lang.modules" % "sbt-scala-module" % "2.2.4")
-addSbtPlugin("ch.epfl.lamp"           % "sbt-dotty"        % "0.5.3")  // cross-compile for dotty
+addSbtPlugin("org.scala-lang.modules" % "sbt-scala-module"   % "2.2.4")
+addSbtPlugin("ch.epfl.lamp"           % "sbt-dotty"          % "0.5.4")      // cross-compile for dotty
+addSbtPlugin("ch.epfl.scala"          % "sbt-version-policy" % "1.0.0-RC5")