adde 'marker' type

marker.go

@@ -0,0 +1,81 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"strings"
+)
+
+func applyMarkerPatch(targetFilePath string, modifications []string) error {
+	// Parse patch content
+	var marker string
+	var entriesToAdd []string
+	var entriesToRemove []string
+	collecting := false
+
+	for _, line := range modifications {
+		switch {
+		case strings.HasPrefix(line, "#"):
+			// Capture marker line (first # line only)
+			if marker == "" {
+				marker = strings.TrimSpace(strings.TrimPrefix(line, "#"))
+				collecting = true
+			}
+		case collecting && strings.HasPrefix(line, "+"):
+			entriesToAdd = append(entriesToAdd, strings.TrimPrefix(line, "+"))
+		case collecting && strings.HasPrefix(line, "-"):
+			entriesToRemove = append(entriesToRemove, strings.TrimPrefix(line, "-"))
+		}
+	}
+
+	// Validate input
+	if marker == "" {
+		return fmt.Errorf("missing marker line starting with #")
+	}
+
+	// Read entire file
+	content, err := os.ReadFile(targetFilePath)
+	if err != nil {
+		return fmt.Errorf("failed to read file: %v", err)
+	}
+
+	lines := strings.Split(string(content), "\n")
+	var modifiedLines []string
+	markerFound := false
+
+	for _, line := range lines {
+		// Check if current line is our marker
+		if !markerFound && strings.TrimSpace(line) == marker {
+			markerFound = true
+			modifiedLines = append(modifiedLines, line)
+			// Add new entries immediately after marker
+			modifiedLines = append(modifiedLines, entriesToAdd...)
+			continue
+		}
+
+		// Check if line should be removed
+		keep := true
+		for _, removeLine := range entriesToRemove {
+			if line == removeLine {
+				keep = false
+				break
+			}
+		}
+
+		if keep {
+			modifiedLines = append(modifiedLines, line)
+		}
+	}
+
+	if !markerFound {
+		return fmt.Errorf("marker line not found: %q", marker)
+	}
+
+	// Write directly to target file
+	err = os.WriteFile(targetFilePath, []byte(strings.Join(modifiedLines, "\n")), 0644)
+	if err != nil {
+		return fmt.Errorf("failed to write changes: %v", err)
+	}
+
+	return nil
+}