PlantUML should have an option to overwrite read-only files when new images are generated.
Many version control systems leave files in a read-only state. PlantUML should be able to overwrite these files if desired.
Suggestion: PlantUML should check if any of the image files being generated exist and are read-only. If they are, it should prompt the user before overwriting with something like the following:
The file "Image.jpg" is read-only. Do you want to overwrite it?
Yes / No / Overwrite All / Overwrite None