output binary in local build

Signed-off-by: Pablo Chacin <pablochacin@gmail.com>

cmd/local/local.go

@@ -5,6 +5,8 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"io"
+	"net/url"
 	"os"
 	"strings"
 
@@ -18,7 +20,8 @@ var ErrTargetPlatformUndefined = errors.New("target platform is required") //nol
 
 const (
 	long = `
-k6build local builder returns artifacts that satisfies certain dependencies
+k6build local builder creates a custom k6 binary artifacts that satisfies certain
+dependencies. Requires the golang toolchain and git.
 `
 
 	example = `
@@ -43,17 +46,19 @@ k6build local -k v0.50.0 -e GOPROXY=http://localhost:80
 )
 
 // New creates new cobra command for local build command.
-func New() *cobra.Command {
+func New() *cobra.Command { //nolint:funlen
 	var (
+		config   local.BuildServiceConfig
 		deps     []string
 		k6       string
+		output   string
 		platform string
-		config   local.BuildServiceConfig
+		quiet    bool
 	)
 
 	cmd := &cobra.Command{
 		Use:     "local",
-		Short:   "build using a local builder",
+		Short:   "build custom k6 binary locally",
 		Long:    long,
 		Example: example,
 		// prevent the usage help to printed to stderr when an error is reported by a subcommand
@@ -80,11 +85,35 @@ func New() *cobra.Command {
 				return fmt.Errorf("building %w", err)
 			}
 
-			encoder := json.NewEncoder(os.Stdout)
-			encoder.SetIndent("", "  ")
-			err = encoder.Encode(artifact)
+			if !quiet {
+				encoder := json.NewEncoder(os.Stdout)
+				encoder.SetIndent("", "  ")
+				err = encoder.Encode(artifact)
+				if err != nil {
+					return fmt.Errorf("processing object %w", err)
+				}
+			}
+
+			binaryURL, err := url.Parse(artifact.URL)
+			if err != nil {
+				return fmt.Errorf("malformed URL %w", err)
+			}
+			artifactBinary, err := os.Open(binaryURL.Path)
+			if err != nil {
+				return fmt.Errorf("opening output file %w", err)
+			}
+			defer func() {
+				_ = artifactBinary.Close()
+			}()
+
+			binary, err := os.OpenFile(output, os.O_WRONLY|os.O_CREATE, 0o755) //nolint:gosec
+			if err != nil {
+				return fmt.Errorf("opening output file %w", err)
+			}
+
+			_, err = io.Copy(binary, artifactBinary)
 			if err != nil {
-				return fmt.Errorf("processing object %w", err)
+				return fmt.Errorf("copying artifact %w", err)
 			}
 
 			return nil
@@ -100,6 +129,8 @@ func New() *cobra.Command {
 	cmd.Flags().BoolVarP(&config.Verbose, "verbose", "v", false, "print build process output")
 	cmd.Flags().BoolVarP(&config.CopyGoEnv, "copy-go-env", "g", true, "copy go environment")
 	cmd.Flags().StringToStringVarP(&config.BuildEnv, "env", "e", nil, "build environment variables")
+	cmd.Flags().StringVarP(&output, "output", "o", "k6", "path to put the binary as an executable.")
+	cmd.Flags().BoolVarP(&quiet, "quiet", "q", false, "don't print artifact's details")
 
 	return cmd
 }