cmd/gomote: fix up printed test commands

Make the test commands easier to just use directly:
- Fix std packages having the wrong directory.
- Add GOMOTE_GROUP prefix if the instances were created in a group.
- Add the instance name (just the first) to the command if not created
  in a group.

Change-Id: I1dffde676a51e69100a1ea8a902c4a67cbde6fce
Reviewed-on: https://go-review.googlesource.com/c/build/+/614161
Reviewed-by: Michael Pratt <mpratt@google.com>
Reviewed-by: Damien Neil <dneil@google.com>
Auto-Submit: Michael Knyszek <mknyszek@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

cmd/gomote/create.go

@@ -147,7 +147,7 @@ func create(args []string) error {
 		fs.Usage()
 	}
 	builderType := fs.Arg(0)
-	_, err := createInstances(context.Background(), builderType, &cfg)
+	_, _, err := createInstances(context.Background(), builderType, &cfg)
 	return err
 }
 
@@ -159,20 +159,20 @@ type createConfig struct {
 	useGolangbuild bool
 }
 
-func createInstances(ctx context.Context, builderType string, cfg *createConfig) ([]string, error) {
+func createInstances(ctx context.Context, builderType string, cfg *createConfig) ([]string, *groupData, error) {
 	var groupMu sync.Mutex
 	group := activeGroup
 	var err error
 	if cfg.newGroup != "" {
 		group, err = doCreateGroup(cfg.newGroup)
 		if err != nil {
-			return nil, err
+			return nil, nil, err
 		}
 	}
 	if group == nil && os.Getenv("GOMOTE_GROUP") != "" {
 		group, err = doCreateGroup(os.Getenv("GOMOTE_GROUP"))
 		if err != nil {
-			return nil, err
+			return nil, nil, err
 		}
 	}
 
@@ -275,12 +275,12 @@ func createInstances(ctx context.Context, builderType string, cfg *createConfig)
 		})
 	}
 	if err := eg.Wait(); err != nil {
-		return nil, err
+		return nil, nil, err
 	}
 	if group != nil {
 		if err := storeGroup(group); err != nil {
-			return nil, err
+			return nil, nil, err
 		}
 	}
-	return instances, nil
+	return instances, group, nil
 }

cmd/gomote/repro.go

@@ -144,15 +144,15 @@ func repro(args []string) error {
 	log.Printf("Selected build %d to initialize the gomote.", gomoteReproID)
 
 	log.Printf("Creating %d instance(s) of type %s...", cfg.count, gomoteBuilderType)
-	instances, err := createInstances(ctx, gomoteBuilderType, &cfg)
+	instances, group, err := createInstances(ctx, gomoteBuilderType, &cfg)
 	if err != nil {
 		return err
 	}
 	log.Printf("Initializing %d instance(s) with environment of %d...", len(instances), gomoteReproID)
 	if err := initReproInstances(ctx, instances, gomoteReproID); err != nil {
 		return err
 	}
-	return printTestCommands(ctx, hc, build)
+	return printTestCommands(ctx, hc, build, instances, group)
 }
 
 func initReproInstances(ctx context.Context, instances []string, reproBuildID int64) error {
@@ -205,7 +205,7 @@ func initReproInstances(ctx context.Context, instances []string, reproBuildID in
 	return eg.Wait()
 }
 
-func printTestCommands(ctx context.Context, hc *http.Client, build *bbpb.Build) error {
+func printTestCommands(ctx context.Context, hc *http.Client, build *bbpb.Build, instances []string, group *groupData) error {
 	// Figure out what project this build is for.
 	props := build.Input.Properties.AsMap()
 	projValue, ok := props["project"]
@@ -279,24 +279,33 @@ func printTestCommands(ctx context.Context, hc *http.Client, build *bbpb.Build)
 			if strings.HasPrefix(rest, project) {
 				t.path = "./x_" + rest
 			} else {
-				// We are almsot definitely unable to run this test -- something went very wrong.
+				// We are almost definitely unable to run this test -- something went very wrong.
 				unknownTests = append(unknownTests, result.TestId)
 			}
+		} else {
+			// Assume it's a std test.
+			t.path = "goroot/src/" + t.pkg
 		}
 		if bench {
 			benchmarks = append(benchmarks, t)
 		} else {
 			tests = append(tests, t)
 		}
 	}
+	prefix := ""
+	instName := " " + instances[0]
+	if group != nil {
+		prefix = "GOMOTE_GROUP=" + group.Name + " "
+		instName = ""
+	}
 	for _, t := range tests {
-		log.Printf("$ gomote run -dir %s goroot/bin/go test -run='%s' .", t.pkgPath(), t.regexp())
+		log.Printf("$ %sgomote run%s -dir %s goroot/bin/go test -run='%s' .", prefix, instName, t.pkgPath(), t.regexp())
 	}
 	for _, t := range benchmarks {
-		log.Printf("$ gomote run -dir %s goroot/bin/go test -run='^$' -bench='%s' .", t.pkgPath(), t.regexp())
+		log.Printf("$ %sgomote run%s -dir %s goroot/bin/go test -run='^$' -bench='%s' .", prefix, instName, t.pkgPath(), t.regexp())
 	}
 	for _, pkg := range specialPackages {
-		log.Printf("$ gomote run -dir ./goroot goroot/bin/go tool dist test %s", pkg)
+		log.Printf("$ %sgomote run%s -dir ./goroot goroot/bin/go tool dist test %s", prefix, instName, pkg)
 	}
 	for _, pkg := range packageFailures {
 		log.Printf("Note: Found package-level test failure for %s.", pkg)