I can tell you from my experience working with text projects, and from working with Arbed: images are referred to by SaveInfo, FullPath and PartialPath, the latter being the path relative to the project file.
If you move the project, including the images relative to the project, to a different folder, everything should still work.
If you use Save As to save your project into a new location, all the PartialPaths get updated to point to the original image, using ../ to ascend from the new location to the common folder in both the old and new location and then descending again to the original image. No images get saved to the new location, not with binary projects, and not with text projects.
I never observed images added to a project that were not saved in a folder below the project folder. So I don’t know, how those get treated.
The best advice, in my opinion, is to use File > Collect Project Items when preparing your project for git to ensure that everything is copied to a single directory and paths are relative to the project file. Then, if you wish, you can remove the resulting “Plugins” and “Scripts” subdirectories. From that point forward, add any images you wish to use in your project to the images folder created by the IDE and the IDE’s default of using relative paths usually* handles everything correctly
*There have, in the past, been instances of the IDE freaking out a bit and generating invalid paths that look something like ../../../../../../../../../file.png.