Make tlPrePrBotHook a task

core/src/main/scala/org/typelevel/sbt/TypelevelPlugin.scala

@@ -20,6 +20,7 @@ import sbt._, Keys._
 import org.typelevel.sbt.gha.GenerativePlugin
 import org.typelevel.sbt.gha.GitHubActionsPlugin
 import de.heikoseeberger.sbtheader.HeaderPlugin
+import org.scalafmt.sbt.ScalafmtPlugin
 
 import scala.collection.immutable
 
@@ -30,13 +31,17 @@ object TypelevelPlugin extends AutoPlugin {
       TypelevelSettingsPlugin &&
       TypelevelCiReleasePlugin &&
       GitHubActionsPlugin &&
-      HeaderPlugin
+      HeaderPlugin &&
+      ScalafmtPlugin
 
   override def trigger = allRequirements
 
   object autoImport {
     lazy val tlFatalWarningsInCi = settingKey[Boolean](
       "Convert compiler warnings into errors under CI builds (default: true)")
+
+    lazy val tlPrePrBotHook =
+      taskKey[Unit]("A hook for bots like Scala Steward to run prePR commands")
   }
 
   import autoImport._
@@ -45,6 +50,8 @@ object TypelevelPlugin extends AutoPlugin {
   import TypelevelSonatypeCiReleasePlugin.autoImport._
   import GenerativePlugin.autoImport._
   import GitHubActionsPlugin.autoImport._
+  import HeaderPlugin.autoImport._
+  import ScalafmtPlugin.autoImport._
 
   override def globalSettings = Seq(
     tlFatalWarningsInCi := true
@@ -99,8 +106,17 @@ object TypelevelPlugin extends AutoPlugin {
     )
   )
 
-  // override for bincompat
-  override def projectSettings = immutable.Seq.empty
+  // immutable.Seq for bincompat
+  override def projectSettings = immutable.Seq(
+    tlPrePrBotHook := Def
+      .sequential(
+        githubWorkflowGenerate,
+        headerCreateAll,
+        scalafmtAll,
+        scalafmtSbt
+      )
+      .value
+  )
 
   private val primaryJavaCond = Def.setting {
     val java = githubWorkflowJavaVersions.value.head