cmd/gomote: add -new-group flag to create

This flag creates a new group for the newly-created instances.

For golang/go#53956.

Change-Id: Ib65a6391a554dbeb1f6f0e44c286ad5b0d221757
Reviewed-on: https://go-review.googlesource.com/c/build/+/418302
Run-TryBot: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>

cmd/gomote/create.go

@@ -164,6 +164,8 @@ func create(args []string) error {
 	fs.IntVar(&count, "count", 1, "number of instances to create")
 	var setup bool
 	fs.BoolVar(&setup, "setup", false, "set up the instance by pushing GOROOT and building the Go toolchain")
+	var newGroup string
+	fs.StringVar(&newGroup, "new-group", "", "also create a new group and add the new instances to it")
 
 	fs.Parse(args)
 	if fs.NArg() != 1 {
@@ -180,7 +182,15 @@ func create(args []string) error {
 		}
 	}
 
-	var activeGroupMu sync.Mutex
+	var groupMu sync.Mutex
+	group := activeGroup
+	if newGroup != "" {
+		group, err = doCreateGroup(newGroup)
+		if err != nil {
+			return err
+		}
+	}
+
 	eg, ctx := errgroup.WithContext(context.Background())
 	client := gomoteServerClient(ctx)
 	for i := 0; i < count; i++ {
@@ -207,10 +217,10 @@ func create(args []string) error {
 				}
 			}
 			fmt.Println(inst)
-			if activeGroup != nil {
-				activeGroupMu.Lock()
-				activeGroup.Instances = append(activeGroup.Instances, inst)
-				activeGroupMu.Unlock()
+			if group != nil {
+				groupMu.Lock()
+				group.Instances = append(group.Instances, inst)
+				groupMu.Unlock()
 			}
 			if !setup {
 				return nil
@@ -239,8 +249,8 @@ func create(args []string) error {
 	if err := eg.Wait(); err != nil {
 		return err
 	}
-	if activeGroup != nil {
-		return storeGroup(activeGroup)
+	if group != nil {
+		return storeGroup(group)
 	}
 	return nil
 }

cmd/gomote/group.go

@@ -57,16 +57,16 @@ func createGroup(args []string) error {
 	if len(args) != 1 {
 		usage()
 	}
-	name := args[0]
+	_, err := doCreateGroup(args[0])
+	return err
+}
+
+func doCreateGroup(name string) (*groupData, error) {
 	if _, err := loadGroup(name); err == nil {
-		return fmt.Errorf("group %q already exists", name)
+		return nil, fmt.Errorf("group %q already exists", name)
 	}
-	if err := storeGroup(&groupData{
-		Name: name,
-	}); err != nil {
-		return err
-	}
-	return nil
+	g := &groupData{Name: name}
+	return g, storeGroup(g)
 }
 
 func destroyGroup(args []string) error {