Suggest user to update scala-cli by package manager in doctor (#1069)

* Suggest user to update scala-cli by package manager in doctor

Author: lwronski

modules/cli/src/main/scala/scala/cli/commands/Doctor.scala

@@ -67,10 +67,15 @@ object Doctor extends ScalaCommand[DoctorOptions] {
       println(
         s"scala-cli would not be able to update itself since it is installed in multiple directories: ${scalaCliPaths.mkString(", ")}."
       )
+    else if (Update.isScalaCLIInstalledByInstallationScript())
+      println(
+        s"scala-cli could update itself since it is correctly installed in only one location: ${scalaCliPaths.mkString}."
+      )
     else
       println(
-        s"scala-cli could update itself since it is correctly installed in only one location: $scalaCliPaths."
+        s"scala-cli can be updated by your package manager since it is correctly installed in only one location: ${scalaCliPaths.mkString}."
       )
+
   }
 
   private def checkNativeDependencies(): Unit = {

modules/cli/src/main/scala/scala/cli/commands/Update.scala

@@ -156,16 +156,20 @@ object Update extends ScalaCommand[UpdateOptions] {
   }
 
   def checkUpdateSafe(logger: Logger): Unit =
-    try {
-      val classesDir =
-        getClass.getProtectionDomain.getCodeSource.getLocation.toURI.toString
-      val binRepoDir = build.Directories.default().binRepoDir.toString()
+    try
       // log about update only if scala-cli was installed from installation script
-      if (classesDir.contains(binRepoDir))
+      if (isScalaCLIInstalledByInstallationScript())
         checkUpdate(UpdateOptions(isInternalRun = true))
-    }
     catch {
       case NonFatal(ex) =>
         logger.debug(s"Ignoring error during checking update: $ex")
     }
+
+  def isScalaCLIInstalledByInstallationScript(): Boolean = {
+    val classesDir =
+      getClass.getProtectionDomain.getCodeSource.getLocation.toURI.toString
+    val binRepoDir = build.Directories.default().binRepoDir.toString()
+
+    classesDir.contains(binRepoDir)
+  }
 }