Add support for SSH config includes

- Support Include directive in SSH config files
- Handle glob patterns (e.g., Include ~/.ssh/config.d/*)
- Prevent circular includes with cycle detection
- Gracefully handle missing or invalid include files
- Maintain compatibility with existing config parsing

This allows users to organize their SSH configs across multiple files
as supported by OpenSSH.

Co-authored-by: Ona <no-reply@ona.com>

ssh_config.go

@@ -42,9 +42,27 @@ func (sc *SSHConfig) LoadConfig() error {
 
 // LoadConfigFromFile loads SSH configuration from a specific file
 func (sc *SSHConfig) LoadConfigFromFile(path string) error {
+	return sc.loadConfigFromFileRecursive(path, make(map[string]bool))
+}
+
+// loadConfigFromFileRecursive loads SSH config with include support and cycle detection
+func (sc *SSHConfig) loadConfigFromFileRecursive(path string, visited map[string]bool) error {
+	// Resolve absolute path to detect cycles
+	absPath, err := filepath.Abs(path)
+	if err != nil {
+		return fmt.Errorf("failed to resolve path %s: %w", path, err)
+	}
+
+	// Check for cycles
+	if visited[absPath] {
+		return fmt.Errorf("circular include detected: %s", absPath)
+	}
+	visited[absPath] = true
+	defer delete(visited, absPath)
+
 	file, err := os.Open(path)
 	if err != nil {
-		return fmt.Errorf("failed to open SSH config file: %w", err)
+		return fmt.Errorf("failed to open SSH config file %s: %w", path, err)
 	}
 	defer file.Close()
 
@@ -68,6 +86,12 @@ func (sc *SSHConfig) LoadConfigFromFile(path string) error {
 		value := strings.Join(parts[1:], " ")
 
 		switch key {
+		case "include":
+			// Handle include directive
+			if err := sc.processInclude(value, visited); err != nil {
+				// Log error but continue processing
+				fmt.Fprintf(os.Stderr, "Warning: failed to process include %s: %v\n", value, err)
+			}
 		case "host":
 			// Save previous host if exists
 			if currentHost != nil {
@@ -103,7 +127,40 @@ func (sc *SSHConfig) LoadConfigFromFile(path string) error {
 	}
 
 	if err := scanner.Err(); err != nil {
-		return fmt.Errorf("error reading SSH config file: %w", err)
+		return fmt.Errorf("error reading SSH config file %s: %w", path, err)
+	}
+
+	return nil
+}
+
+// processInclude handles SSH config include directives
+func (sc *SSHConfig) processInclude(pattern string, visited map[string]bool) error {
+	// Expand tilde to home directory
+	if strings.HasPrefix(pattern, "~/") {
+		homeDir, err := os.UserHomeDir()
+		if err != nil {
+			return fmt.Errorf("failed to get home directory: %w", err)
+		}
+		pattern = filepath.Join(homeDir, pattern[2:])
+	}
+
+	// Handle glob patterns
+	matches, err := filepath.Glob(pattern)
+	if err != nil {
+		return fmt.Errorf("invalid glob pattern %s: %w", pattern, err)
+	}
+
+	// Process each matching file
+	for _, match := range matches {
+		// Skip directories
+		if info, err := os.Stat(match); err == nil && info.IsDir() {
+			continue
+		}
+
+		// Recursively load the included file
+		if err := sc.loadConfigFromFileRecursive(match, visited); err != nil {
+			return fmt.Errorf("failed to load included file %s: %w", match, err)
+		}
 	}
 
 	return nil