Improve launch options for AppImage desktop integration, especially during AppImage updates.

[Renkoto]

Currently with the current AppImage integration programs (Gear Lever, AppImage Launcher and others) there is a very annoying issue, when you update an AppImage also overwrites the . desktop file that is automatically generated in $HOME/. local/share/applications without the user’s consent, so any changes to the launch options on the .desktop file made by the user will be lost and the user will have to re-add them manually.

This is a problem for those looking to start another program along with the AppImage, such as using mangohud on OpenGL applications (the MANGOHUD environment variable only works with Vulkan applications) and/or want to use firejail to confine an AppImage, as the current launch options setting in Gear Lever is only for running launch arguments after the AppImage has been launched.

This could be implemented in several ways, but the ones I'm thinking about right now are:

• Add another launch options box that runs before the application and allow custom launch options to persist after updates
• Alternatively a confirmation checkbox option (per app) to prevent the. desktop file to be overwritten when updating the AppImage from Gear Lever

I hope I've been able to explain myself well, English is not my native language. :P