cleanup/refactor: Re-generate Alpha command

- Refactored the `rescaffold` command to improve error handling, encapsulate logic, and streamline execution flow.
- Moved the code implementation from `pkg` to the CLI since it pertains directly to a command.

pkg/cli/alpha/command.go

@@ -0,0 +1,48 @@
+/*
+Copyright 2023 The Kubernetes Authors.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+	http://www.apache.org/licenses/LICENSE-2.0
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package alpha
+
+import (
+	log "github.com/sirupsen/logrus"
+	"github.com/spf13/cobra"
+)
+
+// NewScaffoldCommand return a new scaffold command
+func NewScaffoldCommand() *cobra.Command {
+	opts := Generate{}
+	scaffoldCmd := &cobra.Command{
+		Use:   "generate",
+		Short: "Re-scaffold an existing Kuberbuilder project",
+		Long: `It's an experimental feature that has the purpose of re-scaffolding the whole project from the scratch 
+using the current version of KubeBuilder binary available.
+# make sure the PROJECT file is in the 'input-dir' argument, the default is the current directory.
+$ kubebuilder alpha generate --input-dir="./test" --output-dir="./my-output"
+Then we will re-scaffold the project by Kubebuilder in the directory specified by 'output-dir'.
+		`,
+		PreRunE: func(_ *cobra.Command, _ []string) error {
+			return opts.Validate()
+		},
+		Run: func(_ *cobra.Command, _ []string) {
+			if err := opts.Generate(); err != nil {
+				log.Fatalf("Failed to command %s", err)
+			}
+		},
+	}
+	scaffoldCmd.Flags().StringVar(&opts.InputDir, "input-dir", "",
+		"path to a Kubebuilder project file if not in the current working directory")
+	scaffoldCmd.Flags().StringVar(&opts.OutputDir, "output-dir", "",
+		"path to output the scaffolding. defaults a directory in the current working directory")
+
+	return scaffoldCmd
+}