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/git/git.go

@@ -0,0 +1,94 @@
+package git
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+)
+
+const (
+	GitDir      = ".git"
+	GitLocalDir = ".gitlocal"
+)
+
+// IsGitRepo checks if the path contains a .git directory
+func IsGitRepo(path string) bool {
+	gitPath := filepath.Join(path, GitDir)
+	info, err := os.Stat(gitPath)
+	if err != nil {
+		return false
+	}
+	return info.IsDir()
+}
+
+// IsGitLocalRepo checks if the path contains a .gitlocal directory
+func IsGitLocalRepo(path string) bool {
+	gitLocalPath := filepath.Join(path, GitLocalDir)
+	info, err := os.Stat(gitLocalPath)
+	if err != nil {
+		return false
+	}
+	return info.IsDir()
+}
+
+// GetRemoteURL returns the remote URL for the git repo
+func GetRemoteURL(gitDir string) string {
+	cmd := exec.Command("git", "--git-dir", gitDir, "remote", "get-url", "origin")
+	output, err := cmd.Output()
+	if err != nil {
+		return ""
+	}
+	return strings.TrimSpace(string(output))
+}
+
+// GetCurrentBranch returns the current branch for the git repo
+func GetCurrentBranch(gitDir string) string {
+	cmd := exec.Command("git", "--git-dir", gitDir, "branch", "--show-current")
+	output, err := cmd.Output()
+	if err != nil {
+		return ""
+	}
+	return strings.TrimSpace(string(output))
+}
+
+// Convert renames .git to .gitlocal
+func Convert(path string) error {
+	gitPath := filepath.Join(path, GitDir)
+	gitLocalPath := filepath.Join(path, GitLocalDir)
+
+	if !IsGitRepo(path) {
+		return fmt.Errorf("no .git directory found at %s", path)
+	}
+
+	if IsGitLocalRepo(path) {
+		return fmt.Errorf(".gitlocal already exists at %s", path)
+	}
+
+	if err := os.Rename(gitPath, gitLocalPath); err != nil {
+		return fmt.Errorf("failed to rename .git to .gitlocal: %w", err)
+	}
+
+	return nil
+}
+
+// Revert renames .gitlocal back to .git
+func Revert(path string) error {
+	gitPath := filepath.Join(path, GitDir)
+	gitLocalPath := filepath.Join(path, GitLocalDir)
+
+	if !IsGitLocalRepo(path) {
+		return fmt.Errorf("no .gitlocal directory found at %s", path)
+	}
+
+	if IsGitRepo(path) {
+		return fmt.Errorf(".git already exists at %s", path)
+	}
+
+	if err := os.Rename(gitLocalPath, gitPath); err != nil {
+		return fmt.Errorf("failed to rename .gitlocal to .git: %w", err)
+	}
+
+	return nil
+}