Add scala3/sbt2 crossbuild, raise 2.12 sbt minversion

build.sbt

@@ -8,7 +8,12 @@ startYear := Some(2011)
 homepage := scmInfo.value map (_.browseUrl)
 scmInfo := Some(ScmInfo(url("https://github.com/sbt/sbt-git"), "scm:git:[email protected]:sbt/sbt-git.git"))
 
-crossSbtVersions := List("1.3.13")
+crossSbtVersions := List("1.5.8")
+
+lazy val scala212 = "2.12.20"
+lazy val scala3 = "3.3.4"
+
+crossScalaVersions := Seq(scala212, scala3)
 
 enablePlugins(GitVersioning, SbtPlugin)
 git.baseVersion := "1.0"
@@ -19,4 +24,11 @@ libraryDependencies ++= Seq(
   "org.scalameta" %% "munit" % "1.0.2" % Test
 )
 
+(pluginCrossBuild / sbtVersion) := {
+  scalaBinaryVersion.value match {
+    case "2.12" => "1.5.8"
+    case _      => "2.0.0-M2"
+  }
+}
+
 scriptedLaunchOpts += s"-Dproject.version=${version.value}"