feat: default to standard output for the merge command (#34)

tools/cli/internal/cli/merge/merge.go

@@ -15,6 +15,8 @@
 package merge
 
 import (
+	"bytes"
+	"encoding/json"
 	"fmt"
 	"log"
 
@@ -25,10 +27,6 @@ import (
 	"github.com/spf13/cobra"
 )
 
-const (
-	DefaultOutputFileName = "FOAS.json"
-)
-
 type Opts struct {
 	Merger        openapi.Merger
 	fs            afero.Fs
@@ -48,6 +46,10 @@ func (o *Opts) Run() error {
 		return err
 	}
 
+	if o.outputPath == "" {
+		return prettyPrintJson(federatedBytes)
+	}
+
 	return o.saveFile(federatedBytes)
 }
 
@@ -65,6 +67,15 @@ func (o *Opts) PreRunE(_ []string) error {
 	return err
 }
 
+func prettyPrintJson(jsonBytes []byte) error {
+	var prettyJSON bytes.Buffer
+	if err := json.Indent(&prettyJSON, jsonBytes, "", "    "); err != nil {
+		return err
+	}
+	fmt.Println(prettyJSON.String())
+	return nil
+}
+
 func (o *Opts) saveFile(data []byte) error {
 	if err := afero.WriteFile(o.fs, o.outputPath, data, 0o600); err != nil {
 		return err
@@ -95,6 +106,6 @@ func Builder() *cobra.Command {
 
 	cmd.Flags().StringVarP(&opts.basePath, flag.Base, flag.BaseShort, "", usage.Base)
 	cmd.Flags().StringArrayVarP(&opts.externalPaths, flag.External, flag.ExternalShort, nil, usage.External)
-	cmd.Flags().StringVarP(&opts.outputPath, flag.Output, flag.OutputShort, DefaultOutputFileName, usage.Output)
+	cmd.Flags().StringVarP(&opts.outputPath, flag.Output, flag.OutputShort, "", usage.Output)
 	return cmd
 }