func main()

in cmd/upload/upload.go [50:179]
115 lines of code
32 McCabe index (conditional complexity)

func main() {
	flag.Usage = func() {
		fmt.Fprintf(os.Stderr, `Usage: upload [--public] [--file=...] <bucket/object>

If <bucket/object> is of the form "golang/go1.4-bootstrap-20yymmdd.tar.gz",
then the current release-branch.go1.4 is uploaded from Gerrit, with each
tar entry filename beginning with the prefix "go/".

`)
		flag.PrintDefaults()
	}
	flag.Parse()
	if flag.NArg() != 1 {
		flag.Usage()
		os.Exit(1)
	}
	args := strings.SplitN(flag.Arg(0), "/", 2)
	if len(args) != 2 {
		flag.Usage()
		os.Exit(1)
	}
	if strings.HasPrefix(*file, "go:") {
		buildGoTarget()
	}
	bucket, object := args[0], args[1]

	// Special support for auto-tarring up Go 1.4 tarballs from the 1.4 release branch.
	is14Src := bucket == "golang" && go14BootstrapRx.MatchString(object)
	if is14Src {
		if *file != "-" {
			log.Fatalf("invalid use of --file with Go 1.4 tarball %v", object)
		}
		*doGzip = true
		*public = true
		*cacheable = true
	}

	if *doGzip && !strings.HasSuffix(object, ".gz") {
		log.Fatalf("--gzip flag requires object ending in .gz")
	}

	proj := *project
	if proj == "" {
		proj, _ = bucketProject[bucket]
		if proj == "" {
			log.Fatalf("bucket %q doesn't have an associated project in upload.go", bucket)
		}
	}

	ctx := context.Background()
	storageClient, err := storage.NewClient(ctx)
	if err != nil {
		log.Fatalf("storage.NewClient: %v", err)
	}

	if is14Src {
		_, err := storageClient.Bucket(bucket).Object(object).Attrs(context.Background())
		if err != storage.ErrObjectNotExist {
			if err == nil {
				log.Fatalf("object %v already exists; refusing to overwrite.", object)
			}
			log.Fatalf("error checking for %v: %v", object, err)
		}
	} else if alreadyUploaded(storageClient, bucket, object) {
		if *verbose {
			log.Printf("Already uploaded.")
		}
		return
	}

	w := storageClient.Bucket(bucket).Object(object).NewWriter(ctx)
	// If you don't give the owners access, the web UI seems to
	// have a bug and doesn't have access to see that it's public, so
	// won't render the "Shared Publicly" link. So we do that, even
	// though it's dumb and unnecessary otherwise:
	w.ACL = append(w.ACL, storage.ACLRule{Entity: storage.ACLEntity("project-owners-" + proj), Role: storage.RoleOwner})
	if *public {
		w.ACL = append(w.ACL, storage.ACLRule{Entity: storage.AllUsers, Role: storage.RoleReader})
		if !*cacheable {
			w.CacheControl = "no-cache"
		}
	}
	var content io.Reader
	switch {
	case is14Src:
		content = generate14Tarfile()
	case *file == "-":
		content = os.Stdin
	default:
		content, err = os.Open(*file)
		if err != nil {
			log.Fatal(err)
		}
	}
	if *doGzip {
		var zbuf bytes.Buffer
		zw := gzip.NewWriter(&zbuf)
		if _, err := io.Copy(zw, content); err != nil {
			log.Fatalf("compressing content: %v", err)
		}
		if err := zw.Close(); err != nil {
			log.Fatalf("gzip.Close: %v", err)
		}
		content = &zbuf
	}

	const maxSlurp = 1 << 20
	var buf bytes.Buffer
	n, err := io.CopyN(&buf, content, maxSlurp)
	if err != nil && err != io.EOF {
		log.Fatalf("Error reading from stdin: %v, %v", n, err)
	}
	if *doGzip {
		w.ContentType = "application/octet-stream"
	} else {
		w.ContentType = http.DetectContentType(buf.Bytes())
	}

	_, err = io.Copy(w, io.MultiReader(&buf, content))
	if cerr := w.Close(); cerr != nil && err == nil {
		err = cerr
	}
	if err != nil {
		log.Fatalf("Write error: %v", err)
	}
	if *verbose {
		log.Printf("Uploaded %v", object)
	}
	os.Exit(0)
}