Adds initial gitlocal CLI and core functionality

Introduces the `gitlocal` command-line tool for managing nested Git repositories.

Includes the following main commands:
- `convert`: Renames `.git` to `.gitlocal`, allowing a parent repository to ignore the converted child repository. Supports recursive scanning and dry-run options. Tracks converted repositories in a global configuration.
- `revert`: Restores `.gitlocal` to `.git`. Includes an option to revert all tracked repositories.
- `status`: Displays a list of all repositories currently tracked by `gitlocal`, showing their path, conversion time, and original remote/branch.

Establishes internal modules for Git operations, configuration management, and recursive repository scanning.
Adds a comprehensive test suite covering core command logic and utility functions.
Initializes Go module and basic project `.gitignore`.

cmd/root.go

@@ -0,0 +1,31 @@
+package cmd
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/spf13/cobra"
+)
+
+var rootCmd = &cobra.Command{
+	Use:   "gitlocal",
+	Short: "Manage nested git repositories",
+	Long: `gitlocal helps you manage nested git repositories by converting .git directories
+to .gitlocal, allowing parent repos to track nested project files.
+
+This is useful when you have a knowledge base or monorepo that contains
+multiple smaller projects, some of which use git locally.`,
+}
+
+func Execute() {
+	if err := rootCmd.Execute(); err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
+}
+
+func init() {
+	rootCmd.AddCommand(convertCmd)
+	rootCmd.AddCommand(revertCmd)
+	rootCmd.AddCommand(statusCmd)
+}