Notify initiating client before shutdown

When a remote client sent the command `shutdown` through the shell, the
client would log an error and exit with a nonzero exit code because
before shutting down, the server would notify the client that it was
disconnecting it due to shutdown. In this scenario, we actually do not
want the client to log an error since they initiated the shutdown, so
before doing the full shutdown, we shutdown the client that inititated
the shutdown with the flag that tells the client not to log the shutdown
or return a nonzero exit code.

main-command/src/main/scala/sbt/internal/client/NetworkClient.scala

@@ -166,6 +166,8 @@ class NetworkClient(
                   console.appendLog(Level.Error, "sbt server disconnected")
                   exitClean.set(false)
                 }
+              } else {
+                console.appendLog(Level.Info, "sbt server disconnected")
               }
               stdinBytes.offer(-1)
               Option(inputThread.get).foreach(_.close())

main/src/main/scala/sbt/internal/CommandExchange.scala

@@ -422,9 +422,14 @@ private[sbt] final class CommandExchange {
                   case _                                     => mt.channel.prompt(ConsolePromptEvent(lastState.get))
                 }
                 commandQueue.add(Exec(t, None, None))
-              case "exit"     => exit(mt)
-              case "shutdown" => shutdown(mt.channel.name)
-              case _          =>
+              case "exit" => exit(mt)
+              case "shutdown" =>
+                channels.find(_.name == mt.channel.name) match {
+                  case Some(c: NetworkChannel) => c.shutdown(false)
+                  case _                       =>
+                }
+                shutdown(mt.channel.name)
+              case _ =>
             }
         }
         if (!isStopped.get) impl()

main/src/main/scala/sbt/internal/server/NetworkChannel.scala

@@ -549,6 +549,15 @@ final class NetworkChannel(
     shutdown(true)
   }
   import sjsonnew.BasicJsonProtocol.BooleanJsonFormat
+
+  /**
+   * Closes down the channel. Before closing the socket, it sends a notification to
+   * the client to shutdown. If the client initiated the shutdown, we don't want the
+   * client to display an error or return a non-zero exit code so we send it a
+   * notification that tells it whether or not to log the shutdown. This can't
+   * easily be done client side because when the client is in interactive session,
+   * it doesn't know commands it has sent to the server.
+   */
   override def shutdown(logShutdown: Boolean): Unit = {
     terminal.close()
     StandardMain.exchange.removeChannel(this)