Introduce an App struct that executes core business logic

The Cobra commands are now a light wrapper around the App struct.

Co-authored-by: Jose Garcia <josebalius@github.com>

cmd/ghcs/main/main.go

@@ -4,22 +4,45 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"net/http"
 	"os"
 
 	"github.com/github/ghcs/cmd/ghcs"
+	"github.com/github/ghcs/cmd/ghcs/output"
+	"github.com/github/ghcs/internal/api"
 	"github.com/spf13/cobra"
 )
 
 func main() {
-	rootCmd := ghcs.NewRootCmd()
+	token := os.Getenv("GITHUB_TOKEN")
+	rootCmd := ghcs.NewRootCmd(ghcs.NewApp(
+		output.NewLogger(os.Stdout, os.Stderr, false),
+		api.New(token, http.DefaultClient),
+	))
+
+	// Require GITHUB_TOKEN through a Cobra pre-run hook so that Cobra's help system for commands can still
+	// function without the token set.
+	oldPreRun := rootCmd.PersistentPreRunE
+	rootCmd.PersistentPreRunE = func(cmd *cobra.Command, args []string) error {
+		if token == "" {
+			return errTokenMissing
+		}
+		if oldPreRun != nil {
+			return oldPreRun(cmd, args)
+		}
+		return nil
+	}
+
 	if cmd, err := rootCmd.ExecuteC(); err != nil {
 		explainError(os.Stderr, err, cmd)
 		os.Exit(1)
 	}
 }
 
+var errTokenMissing = errors.New("GITHUB_TOKEN is missing")
+
 func explainError(w io.Writer, err error, cmd *cobra.Command) {
-	if errors.Is(err, ghcs.ErrTokenMissing) {
+	if errors.Is(err, errTokenMissing) {
 		fmt.Fprintln(w, "The GITHUB_TOKEN environment variable is required. Create a Personal Access Token at https://github.com/settings/tokens/new?scopes=repo")
 		fmt.Fprintln(w, "Make sure to enable SSO for your organizations after creating the token.")
 		return