[FEATURE] Add command-line option to specify a custom configuration file

[rootnotez]

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Please confirm the following points:

• [x] This feature request is NOT for the Android apps in the Play Store
• [x] I have searched the project page to check if a similar request was already made

Application or Project

projectM Standalone SDL2 Frontend (includes the Steam app)

Is Your Enhancement Related to a Problem?

projectMSDL.properties is created in a specific directory, but there is no command line option to override it.

https://github.com/projectM-visualizer/frontend-sdl-cpp/blob/master/README.md?plain=1#L94-L101

Your Suggested Enhancement

Add a command line option to specify a projectMSDL.properties file. Since there is a save option inside the projectMSDL app, may need to check if a config file was passed in, and make a decision whether changes should be saved to the currently loaded file. Perhaps the user could be provided the context of what save file is currently loaded.

I think also maybe copying the default file with the helpful commented out setting descriptions to the user file might be helpful.

Alternative Solutions

No response

Additional Context

No response

[kblaschke]

Had this idea on the back of my mind for some time now, but didn't create a ticket for that. Will add a --config/-c option to specify a custom configuration file that overrides the platform-specific default path. It's super easy to do, so won't take ages to implement 😉