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/scanner/scanner.go

@@ -0,0 +1,59 @@
+package scanner
+
+import (
+	"os"
+	"path/filepath"
+
+	"git.membo.co.uk/dtomlinson/gitlocal/internal/git"
+)
+
+// FindNestedGitRepos recursively scans rootPath for nested .git and .gitlocal directories
+// and returns a list of absolute paths to directories containing .git or .gitlocal
+// It skips the root repo's .git/.gitlocal directory if one exists
+func FindNestedGitRepos(rootPath string) ([]string, error) {
+	var repos []string
+
+	// Get absolute path
+	absRoot, err := filepath.Abs(rootPath)
+	if err != nil {
+		return nil, err
+	}
+
+	// Check if root itself is a git repo (either .git or .gitlocal)
+	rootIsGitRepo := git.IsGitRepo(absRoot) || git.IsGitLocalRepo(absRoot)
+	rootGitPath := filepath.Join(absRoot, git.GitDir)
+	rootGitLocalPath := filepath.Join(absRoot, git.GitLocalDir)
+
+	err = filepath.Walk(absRoot, func(path string, info os.FileInfo, err error) error {
+		if err != nil {
+			return err
+		}
+
+		// Skip if not a directory
+		if !info.IsDir() {
+			return nil
+		}
+
+		// Skip if this is the root's .git or .gitlocal directory
+		if rootIsGitRepo && (path == rootGitPath || path == rootGitLocalPath) {
+			return filepath.SkipDir
+		}
+
+		// Check if this directory is named .git or .gitlocal
+		if info.Name() == git.GitDir || info.Name() == git.GitLocalDir {
+			// Get the parent directory (the actual repo path)
+			repoPath := filepath.Dir(path)
+			repos = append(repos, repoPath)
+			// Skip descending into .git/.gitlocal directory
+			return filepath.SkipDir
+		}
+
+		return nil
+	})
+
+	if err != nil {
+		return nil, err
+	}
+
+	return repos, nil
+}