The proposed use I have for this is for when packages are looking for their Artifacts.toml file, they have to annoying things, and non relocatable ones even more annyoingly. (Maybe we need to add something like @__PKGDIR that does the relocatable thing)

Currently @__DIR__ bakes in the current path of the whenever it's called, but for this it's usually the path of the src directory of a package. Examples of this are the Artifacts.toml file or a examples/directory, The issue arises if one tries to move that package to another place, either via PkgCompiler or via copying the depot around. Those baked in absolute paths mean that it's not safe for this package to be relocatable.

I don't have a clear proposal for this, but I imagine it would just be a expansion of the relocatable package image work done by @fatteneder, specially since if you get the package those files are already there, we just don't have a nice way of getting to them.