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`.

internal/config/config.go

@@ -0,0 +1,111 @@
+package config
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"time"
+
+	"gopkg.in/yaml.v3"
+)
+
+const (
+	ConfigVersion = "1"
+	ConfigFile    = ".gitlocal.yml"
+)
+
+type Repo struct {
+	Path           string    `yaml:"path"`
+	ConvertedAt    time.Time `yaml:"converted_at"`
+	OriginalRemote string    `yaml:"original_remote,omitempty"`
+	OriginalBranch string    `yaml:"original_branch,omitempty"`
+}
+
+type Config struct {
+	Version string `yaml:"version"`
+	Repos   []Repo `yaml:"repos"`
+}
+
+// GetConfigPath returns the absolute path to the config file
+func GetConfigPath() (string, error) {
+	home, err := os.UserHomeDir()
+	if err != nil {
+		return "", fmt.Errorf("failed to get home directory: %w", err)
+	}
+	return filepath.Join(home, ConfigFile), nil
+}
+
+// Load reads the config file or creates a new empty config if it doesn't exist
+func Load() (*Config, error) {
+	configPath, err := GetConfigPath()
+	if err != nil {
+		return nil, err
+	}
+
+	// If config doesn't exist, return empty config
+	if _, err := os.Stat(configPath); os.IsNotExist(err) {
+		return &Config{
+			Version: ConfigVersion,
+			Repos:   []Repo{},
+		}, nil
+	}
+
+	data, err := os.ReadFile(configPath)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read config file: %w", err)
+	}
+
+	var cfg Config
+	if err := yaml.Unmarshal(data, &cfg); err != nil {
+		return nil, fmt.Errorf("failed to parse config file: %w", err)
+	}
+
+	return &cfg, nil
+}
+
+// Save writes the config to disk
+func (c *Config) Save() error {
+	configPath, err := GetConfigPath()
+	if err != nil {
+		return err
+	}
+
+	data, err := yaml.Marshal(c)
+	if err != nil {
+		return fmt.Errorf("failed to marshal config: %w", err)
+	}
+
+	if err := os.WriteFile(configPath, data, 0644); err != nil {
+		return fmt.Errorf("failed to write config file: %w", err)
+	}
+
+	return nil
+}
+
+// AddRepo adds a new repo to the config
+func (c *Config) AddRepo(repo Repo) {
+	// Remove existing entry if it exists
+	c.RemoveRepo(repo.Path)
+	c.Repos = append(c.Repos, repo)
+}
+
+// RemoveRepo removes a repo from the config by path
+func (c *Config) RemoveRepo(path string) {
+	filtered := []Repo{}
+	for _, r := range c.Repos {
+		if r.Path != path {
+			filtered = append(filtered, r)
+		}
+	}
+	c.Repos = filtered
+}
+
+// FindRepo returns a repo by path, or nil if not found
+func (c *Config) FindRepo(path string) *Repo {
+	for _, r := range c.Repos {
+		if r.Path == path {
+			return &r
+		}
+	}
+	return nil
+}